U.S. commanders used the base to coordinate a wide variety of missions during the wars in Iraq and Afghanistan, as well as strikes against the Islamic State in Syria. The Air Force has deployed a wide variety of aircraft there, from advanced fighters and long-range bombers to drones, transport planes and in-flight refueling tankers.

It also became the central evacuation point for tens of thousands of Afghans and Americans who fled Afghanistan in 2021 when the U.S. military withdrew.

The Combined Air Operations Center at the base helps project U.S. air power across a vast region encompassing 21 countries, from Northeast Africa to Central and South Asia, according to the Air Force.

Qatar, which saw the United States as its main protector in the Middle East, finished building the base in 1996, hoping to encourage the deployment of the U.S. military there. Over the years, Qatar has spent at least $8 billion to develop the base, which its military also uses alongside the British Royal Air Force, as part of its efforts to build up its partnership with the United States.

The modernization and expansion of the base has allowed a number of key U.S. military commands to operate out of it. Along with the U.S. Central Command, the base also hosts command facilities for American special forces.

The base’s location was carefully guarded until 2013, when Chuck Hagel, then the defense secretary, lifted the veil of secrecy.

President Trump visited Al Udeid last month while on a four-day tour of Gulf States. There, in a rally-like atmosphere, he spoke about Qatar’s purchases of American military supplies and told several of his favorite stories, including one about his trip to Iraq during his first term.

“I have nothing else to do,” Mr. Trump told U.S. troops from a stage at the base, “so let’s have a little fun.”

They urged field offices to monitor their collection platforms and stay in close contact with the Defense Department, including the National Guard, “who may be targeted for retaliation” while “specific attention should be paid to” U.S. military facilities connected to the strikes in Iran.

In New York City, Mayor Eric Adams said that more police officers would be on duty around religious, cultural and diplomatic sites “out of an abundance of caution,” given the situation in the Middle East.

Iran, which the United States has designated as a state sponsor of terrorism, has long backed a network of militias across the Middle East in an attempt to extend its influence across the region and undermine Israel. Those militias include Hamas, Hezbollah and the Houthis, who control parts of Yemen.

Separately, the Department of Homeland Security issued a security bulletin stating that the “ongoing Iran conflict” had elevated security concerns in the country and adding that cyberattacks by pro-Iranian hackers were likely.

“The likelihood of violent extremists in the homeland independently mobilizing to violence in response to the conflict would likely increase if Iranian leadership issued a religious ruling calling for retaliatory violence against targets in the homeland,” the bulletin said.

It noted that “cyberactors affiliated with the Iranian government may conduct attacks against U.S. networks.”

Such advisories are typical after American forces take significant military action overseas, reflecting a worry by national security officials that people living in the United States may be angry or compelled to lash out. The relationship between Iran and the United States is particularly fraught in recent years, particularly given that U.S. officials have accused Iran of trying to assassinate American officials, as well as Iranian dissidents in the country.

In a conference call on Sunday, D.H.S. and F.B.I. officials cautioned state and local law enforcement officials of the possibility of threats to U.S. communities. During the call, the nonprofit organization Secure Community Network, which provides safety consulting and training for Jewish facilities across North America, said that the level of threats was very high.

“Iran would not strike in the U.S. unless a red line was crossed,” said Michael Masters, the group’s chief executive, according to a summary of the call. “That red line was assessed to be direct military engagement, especially targeting Iran’s nuclear facilities. That red line has now been crossed.”

The bulletin by the Department of Homeland Security said that the Iran-Israel war “could also motivate violent extremists and hate crime perpetrators seeking to attack targets perceived to be Jewish, pro-Israel, or linked to the US government or military in the homeland.”

Former F.B.I. officials said the bureau was well versed in these situations and would ask informants to find out if there were any new threats while scrutinizing existing cases, including possible surveillance of those being investigated.

In its email on Sunday, the F.B.I. said to prioritize tips potentially associated with Iran or its proxies.

Carlos Fernandez, a former senior F.B.I. agent in charge of New York’s counterterrorism division, said the agents had to take seriously the possibility of sleeper cells in the United States, especially since Iran has been accused of plotting to kill President Trump before the election and a human-rights activist in Brooklyn.

Indeed, the bureau has also uncovered members of Hezbollah, who trained in Lebanon but then moved to the United States, where they were eventually arrested in Michigan and New York and charged with terrorism.

“It’s very real,” he said. “It’s a legitimate concern.”

It was unclear why Israel struck the prison. There were no immediate reports of injuries, and Iran said it still had control of the facility.

Here’s what to know about the prison and the Israeli attack:

What is Evin prison?

Thousands of prisoners are held at Evin, among them hundreds of dissidents, including prominent opposition politicians, activists, lawyers, journalists, environmental activists and students. It is also used to hold prominent non-Iranian or dual-citizen prisoners, many of whom have been accused of spying.

The prison sits on a hilltop in northern Tehran at the foot of the Alborz Mountains. The compound is surrounded by electrified barbed-wire fences as well as a minefield.

How was the prison damaged?

IRNA, the Iranian state news agency, reported that projectiles had caused “damage to parts of the facility” but said the prison was “under full control.”

Video footage reviewed by The Times shows rescue workers clearing debris and metal beams collapsed by the strike from a gaping hole in the entrance.

Other footage examined by The Times shows damage to buildings in the immediate aftermath of another explosion by a second entrance to the prison complex, about 600 yards from the main prison entrance. This strike appeared to be by an entrance to a visitation center on the prison grounds.

How did Evin gain its reputation?

The prison was opened in 1971 under Shah Mohammed Reza Pahlavi. Over the next seven years, the facility came to international prominence because of what Human Rights Watch called the “horrifying conditions” in which prisoners were held by the secret police.

A 1979 revolution, set off in part by anger at the autocratic government, overthrew the shah, ushering in a theocratic regime under Ayatollah Ruhollah Khomeini. But the prison’s notoriety grew.

In 1988, thousands of Evin prisoners were executed after cursory trials, according to Human Rights Watch. Many of those killed were viewed as a threat to the new Islamic government.

Several prominent Iranians were detained at Evin during the wave of protests in 2022 that followed the death of Mahsa Amini, a 22-year-old Iranian woman arrested by Iran’s morality police. During the protests, a huge fire broke out at the prison. Residents nearby reported gunshots and explosions amid chants of “death to the dictator,” and IRNA reported at the time that eight people had been injured. The cause of the fire remained unclear.

In April, the European Union placed the head of the prison, Hedayatollah Farzadi, under sanctions.

What are conditions like at the prison?

Former prisoners have described long interrogations, torture, rape, psychological humiliation, solitary confinement and other examples of harsh treatment and abuse.

Executions at the prison have often been conducted by hanging, they say. Female prisoners who have been tortured have also then been denied adequate medical care, according to Amnesty International.

Cecilia Sala, an Italian journalist who was detained in Iran in December and held at the prison before being released, said her cell had two blankets but no mattress or pillow. She said guards seized her glasses, rendering her all but unable to see. The lights in the cell were constantly on, and during daily interrogations, which lasted for hours, she was blindfolded and had to sit facing a wall, she said.

Are foreign prisoners held at Evin?

Iran has used the detention of foreign and dual citizens as a tool of its foreign policy for nearly five decades. Britain, France, the United States and others have accused Iran of detaining their citizens, as well as dual nationals, and using them as diplomatic bargaining chips.

Cécile Kohler and Jacques Paris, two French citizens, were held for over three years at Evin. Their detention has become a sticking point in relations between France and Iran.

Ms. Kohler, 40, a literature professor, and her partner Mr. Paris, a retired professor in his 70s, were visiting Iran as tourists in 2022 when they were arrested on spying charges that France strenuously rejects. Other French citizens arrested on similar charges have been gradually released, leaving Ms. Kohler and Mr. Paris as the only French citizens remaining in Iranian custody.

French authorities have likened the conditions they face in Evin to “torture,” saying they are in near total isolation and have almost no access to consular visits. Last month, France filed a complaint against Iran at the International Court of Justice over their case.

France’s foreign minister, Jean-Noël Barrot, said on Monday that Ms. Kohler and Mr. Paris were unhurt after the Israeli strikes, which he called “unacceptable,” and repeated France’s demand for their release.

Aurelien Breeden and Malachy Browne contributed reporting

Since launching its campaign against Iran earlier this month, the Israeli military has hit Iranian nuclear facilities, scientists and senior military commanders, but it has also struck targets lacking a clear link to Iran’s nuclear program or ballistic missiles, including the state broadcaster.

According to the defense minister’s office, Israel’s strikes in Tehran on Monday targeted the headquarters of the Basij, a volunteer force under the umbrella of the Islamic Revolutionary Guards Corps that has used brutal tactics to crack down on protests in Iran, and Evin prison, the notorious facility holding political prisoners.

Israel also struck access routes to Fordo, the heavily fortified nuclear-enrichment site that the United States bombed on Sunday, the Israeli military said.

President Trump claimed on Sunday that Iran’s nuclear program had been “totally and completely obliterated.” Prime Minister Benjamin Netanyahu of Israel said that the American military caused “very big damage” to Fordo, but he clarified that Israel still did not know the full extent.

Morteza Heidari, the spokesman for crisis management in the province where Fordo is, on Monday reported an “attack on the Fordo nuclear site,” according to the government-affiliated Mehr and Tasnim news agencies. He said there was no danger to the public from the strikes, the news agencies said.

Later on Monday, the Israeli military said it had targeted other forces under the Revolutionary Guards, including ones that it described as being responsible for dealing with domestic threats. It also said it had hit missile and radar production sites and missile storage infrastructure.

The impact and extent of the strikes were not immediately clear. But videos reviewed by The New York Times show clouds of smoke emanating from a metal gate below a sign that reads ‘Evin Detention Facility’ in Farsi.

The reports of the strikes on the Evin prison caused particular concern in France because two French citizens, Cécile Kohler and Jacques Paris, are detained there.

“We are worried that Cécile and Jacques are going to die under bombs,” Noémie Kohler, Ms. Kohler’s sister, told Franceinfo radio on Monday. “We still have no way of contacting them,” she added. “We are absolutely panicked.”

France has accused Iran of detaining Ms. Kohler and Mr. Paris for over three years on baseless spying charges and has repeatedly demanded their release.

The strikes on Evin — which is close to apartment blocks and a popular hiking route — also hit a main power line that caused outages in two large districts of Tehran, according to the national electricity company Tavanir. It said in a statement distributed broadly to government-affiliated news agencies that it was able to repair the outages within an hour.

Iranian news outlets also reported that the Israeli military hit a building near the Iranian Red Crescent Society, an emergency response service. A video posted by the government-affiliated Mehr news agency, and verified by The Times, showed smoke rising in the area. It was not clear what was in the building that had been struck.

Erika Solomon and Sanjana Varghese contributed reporting to this article.

“We are advancing, step by step, to achieve these goals,” he said. “We are very, very close to completing them.”

Mr. Netanyahu did not say when he believed Israel would end its bombing campaign. Nor did he mention another goal that some observers have suggested Israel might be pursuing in Iran: regime change.

Israelis have broadly backed Mr. Netanyahu’s decision to open the offensive against Iran. Even longtime critics of the prime minister — including Yair Lapid, head of Israel’s parliamentary opposition — have praised what they see as the war’s tactical successes.

But as Iran launches missiles in response, the conflict has also paralyzed much of Israel, shuttering schools, businesses and the international airport near Tel Aviv, leaving thousands of Israelis stranded abroad. The economic damage has compounded the cost of more than 20 months of war in Gaza and Lebanon.

Some Israeli analysts and politicians have argued that now is the time to wind down the fighting.

In his address on Sunday night, Mr. Netanyahu said that he would not be dragged into a “war of attrition” with Iran. But Israel would not cease its assault on Iran before it had “accomplished all of its goals,” Mr. Netanyahu vowed, without providing a timetable.

“We will not continue to operate beyond what is necessary to achieve them,” he said. “But we also won’t finish up too soon. When the aims are achieved, the operation will be concluded, and the fighting will stop.”

Some analysts in Israel have suggested that if Mr. Netanyahu’s war against Iran is seen as successful, he could show greater flexibility in talks to end the war with Hamas in Gaza and to free the remaining hostages there. For months, Mr. Netanyahu has seemed unwilling to make concessions in the talks, which his far-right political allies have opposed.

On Sunday, Mr. Netanyahu said that the blows dealt to Iran — a longtime patron of Hamas — would also further weaken the Palestinian armed group in Gaza.

“It will take a bit more time. But there’s no doubt that our great achievements in Iran contribute to achieving the goals in Gaza,” he said.

Johnatan Reiss contributed reporting from Tel Aviv.

“The absolutely unprovoked aggression against Iran is unfounded and unjustified,” Mr. Putin said at a meeting with Iran’s foreign minister, Abbas Araghchi, according to a Kremlin statement. “We are making efforts from our side to provide support to the Iranian people.”

Mr. Putin told Mr. Araghchi that he had spoken about the Israel-Iran war with President Trump, as well as with the leaders of Israel, Iran and the United Arab Emirates. Earlier on Monday, the Kremlin said Mr. Putin also spoke by telephone with Prime Minister Mohammed Shia al-Sudani of Iraq.

The discussions appeared to be part of the Kremlin’s broader efforts to present Russia as a potential mediator in any talks that could bring an end to the fighting.

Yet, according to the Kremlin’s statement on Monday, Mr. Putin stopped short of directly calling out the United States or Israel for attacking Iran. The careful tone contrasted with the more explicit one used by Mr. Araghchi, who denounced the “aggressive actions of Israel and the U.S.A.,” according to the Kremlin.

Dmitri S. Peskov, the Kremlin’s spokesman, attempted to toe the same careful line as Mr. Putin. In remarks on Monday, he voiced Russia’s support for Iran, without making any military or economic commitments that could potentially anger the Trump administration or siphon resources from Russia’s war in Ukraine.

Speaking to reporters, Mr. Peskov deflected a question about whether Russia would be willing to bolster Iranian air defenses.

“Going forward, everything will depend on what Iran will need,” Mr. Peskov said.

He added that Russia had already issued a statement condemning strikes on Iran, and had offered to mediate the conflict.

“These are types of support,” Mr. Peskov said.

Under the terms of the treaty, the European Union and Israel agreed that their relationship “would be based on respect for human rights and democratic principles.”

The review concluded that there are “indications that Israel would be in breach” of those standards, referring to several specific issues. Those included Israeli restrictions of essential goods and food into Gaza; attacks that the report said had caused a “significant number of casualties”; and military strikes on hospitals and medical facilities.

Because E.U. member states are sharply divided on Israel, it could be difficult to achieve the consensus needed to shift the bloc’s policies toward the nation. But the report’s conclusions underscored growing frustrations, including among some of Israel’s closest allies, over the handling of the war in Gaza.

Kaja Kallas, the European Union’s foreign policy chief, presented the review’s findings to a meeting of the bloc’s foreign ministers in Brussels on Monday.

“Our first goal is to change the situation on the ground and help the humanitarian aid to get in and help the people,” Ms. Kallas said in a news conference after the meeting. “Today was the beginning of the debate, and not the end.”

Israel has strongly rejected the findings. The Israeli Foreign Ministry said in a response to the European Union, shared with The New York Times, that the review was “a complete moral and methodological failure.” The ministry pointed out that it “opens with an admission that it lacks the ability to verify its own statements.”

The next steps will be to present the finding to Israel, Ms. Kallas said. If the situation does not improve, officials could discuss other steps at their meeting in July, she added.

“Our main concern is the humanitarian aid distribution,” she said.

The back-and-forth underscored how tense relations between the European Union and Israel have become. The situation has become more complicated after Israel launched a major assault on Iran last week in a bid to cripple its nuclear program, one that now involves the United States: America struck three sites last weekend.

E.U. officials have spoken about the conflict with Iran cautiously, and there are divisions in Europe over how much to support Israel and America’s actions. European officials have widely urged a return to diplomacy to resolve the crisis.

Many European officials and diplomats have emphasized that the conflict with Tehran should not distract from what is happening in Gaza, but the combination of events has left Brussels struggling to agree on a unified stance toward Israel.

“When all the focus is on Iran and the escalation regarding Iran, we should not forget about Gaza and the terrible war that’s taking place there, and the terrible humanitarian situation,” Caspar Veldkamp, the Dutch minister for foreign affairs, told reporters on Monday.

The Netherlands had been vocal in pushing for the review. That was notable, since it had traditionally been seen as centrist on the Israeli-Palestinian conflict, said Hugh Lovatt, a senior fellow at the European Council on Foreign Relations.

“That speaks to the growing frustration and anger amongst a number of European governments,” Mr. Lovatt said, adding that conversations “will continue to happen about other steps, whether it’s banning settlement products and financial services.”

Some member states have pushed for especially serious consequences.

“This is the time for action,” José Manuel Albares Bueno, Spain’s foreign minister, said as he headed into Monday’s meeting. He said he would call for a suspension of the agreement with Israel, along with an embargo on weapon sales to the country.

“Europe must show courage,” he added.

But in the end, the review and its findings might be more symbolically important than practically effective, because E.U. nations remain deeply split on issues related to Israel.

Imposing sanctions or suspending the agreement, for instance, would require unanimity among member states — which is unlikely. The prime minister of Hungary, Viktor Orban, for example, is an ally of Mr. Netanyahu and would almost certainly not agree to impose restrictions on Israel.

Even more modest measures, like peeling back parts of the agreement, would require support from a substantial majority of European nations.

“It’s a complex situation,” Hadja Lahbib, the European commissioner for crisis preparedness, said on Monday.

“We may not agree on the reasons behind and even the consequences of the current crisis, but there is a common denominator that exists,” he said at the meeting of the watchdog, the International Atomic Energy Agency. “First, we don’t want to see a nuclear accident.”

Israel began its military campaign against Iran’s nuclear program and military leadership on June 13. The United States intervened militarily early on Sunday local time, attacking the three Iranian nuclear sites, with President Trump saying that the goal was to prevent Iran from building a nuclear weapon.

American officials have said that while Israel’s intelligence agency believes that Iran can achieve a nuclear weapon in 15 days, American spy agencies believe that it could take several months, and up to a year, for Iran to make a weapon.

The International Atomic Energy Agency declared on June 12 that Iran was not complying with its nuclear nonproliferation obligations. But Mr. Grossi stressed on Monday that the correct approach was diplomacy, and urged a return to negotiations.

“Military escalation not only threatens lives, it also delays us from taking the diplomatic path to achieve the long-term assurance that Iran does not acquire a nuclear weapon,” Mr. Grossi said Monday. Iran insists that its nuclear program is for civilian use, not to develop weapons.

“There has never been a time more important than now to muster the political courage to step away from the edge,” Mr. Grossi said.

Later on Monday, the Israeli military said that it had attacked access routes to the Fordo nuclear enrichment site to obstruct them, a day after the United States struck the site itself. Both Israeli and American officials have said the site was severely damaged in Sunday’s U.S. strikes, but that it would take time for a full damage assessment.

Mr. Grossi said that at this time “no one, including the I.A.E.A.,” is in a position to has fully assessed the damage at Fordo. He added that Iran has informed the agency that there was no increase in off-site radiation levels at any of the three sites hit by the United States.

Senior American officials have conceded that they do not know the fate of Iran’s stockpile of near-bomb-grade uranium. Mr. Grossi said on Monday that Iran’s foreign minister, Abbas Araghchi, had written in a June 13 letter to him that Iran would adopt “special measures” to protect nuclear equipment and materials.

Aaron Boxerman contributed reporting.

In the original post, according to a screenshot by the local TV news station KTLA, the department said “Our hearts go out to the victims and the families impacted by the recent bombings in Iran.”

In its statement on Sunday, the Sheriff’s Department called that post “offensive and inappropriate.”

“This post was unacceptable,” the Sheriff’s Department said, “made in error, and does not reflect the views of Sheriff Robert G. Luna or the Department.”

As a law enforcement agency, the Sheriff’s Department said, it did not comment on “foreign policy or military matters.” It said it was conducting an internal investigation to determine how the post was created and published.

Los Angeles County is home to large populations of both Iranian and Jewish people, including many Iranian Jews.

Of the roughly 400,000 Iranian-born immigrants in the United States, roughly one-third lives in or around Los Angeles, according to the Migration Policy Institute. Westwood, a neighborhood on the west side of Los Angeles near the U.C.L.A. campus, has been nicknamed “Tehrangeles.”

Los Angeles is also home to more than 500,000 Jews, the second-largest Jewish community in the U.S., according to 2021 research by Brandeis University.

The Sheriff’s Department’s social media post emphasized that there was no specific danger for residents but encouraged people to be vigilant.

“At the moment, there are no known threats to Los Angeles County. However, out of an abundance of caution, we are increasing patrol checks at places of worship and other sensitive locations throughout the county,” the sheriff’s department said.

“Ministers are very much focused on the diplomatic solution, and also the concerns of retaliation and this war escalating are huge,” Kaja Kallas, the European Union’s top diplomat, told journalists. Ms. Kallas added that any Iranian closure of the Strait of Hormuz, a key shipping route for oil and gas, would be “extremely dangerous.”

American military and intelligence officials have detected signs that Iran-backed militias were preparing to attack American bases in Iraq, and possibly in Syria, in retaliation for the U.S. strikes in Iran on Sunday, fueling fears that tensions could ramp up. If Tehran were to close access to the Strait of Hormuz, oil prices could soar and some U.S. Navy ships could be pinned in the Persian Gulf, American military officials say.

Ms. Kallas and foreign ministers from Britain, France, and Germany met with Iran’s foreign minister, Abbas Araghchi, in Geneva on Friday. Ms. Kallas said that at that meeting, Iran was opening up to discussions of “nuclear, but also broader security issues that are concerning Europe.”

Still, officials fretted that a peaceful outcome remained far from guaranteed.

“We are very concerned about the risk of an escalation, which could be devastating in the Middle East and have very serious consequences for the stability of the world,” Jean-Noël Barrot, France’s minister for Europe and foreign affairs, said as he headed into Monday’s meeting.

“Europe can bring its experience, its competence, in-depth knowledge of these questions to open a space for negotiation,” he added.

While Mr. Barrot and other European officials suggested that strikes on Iranian nuclear facilities by Israel and the United States might delay nuclear developments, they also said that a negotiated solution would be more durable in the long run.

“At this moment, I think it’s very important to find a way back to the negotiations,” Caspar Veldkamp, the Dutch minister for foreign affairs, told reporters.

In more than a week of fighting between Israel and Iran, Israel’s military has steered clear of hitting Iranian naval assets. So while Iran’s ability to respond to attacks has been severely damaged, it has a robust navy and maintains operatives across the region, where the United States has more than 40,000 troops. Iran also has an array of mines that its navy could lay in the Strait of Hormuz, which hugs a portion of Iran’s southern border.

A quarter of the world’s oil and 20 percent of the world’s liquefied natural gas passes through the Strait of Hormuz, so mining the choke point would cause oil and gas prices to soar. The majority of those fuels go to Asia, meaning that countries there would most likely be severely affected by any closure. The United States and other countries would feel the effects in the form of higher energy costs.

Closing the waterway could isolate American minesweepers in the Persian Gulf on one side of the strait. Two defense officials indicated that the Navy was looking to disperse its ships in the gulf so that they would be less vulnerable. A Navy official declined to comment, citing operational security. The officials spoke on condition of anonymity because they were not authorized to speak publicly.

Even before the U.S. military struck Iranian nuclear sites over the weekend, Iran vowed that it would respond forcefully to any attack by American forces — potentially setting off a cycle of escalation. Since the strikes, Iran appears to be weighing its options.

“Iran is strategically weaker but operationally still lethal across the region, and Americans still have troops across that part of the world,” said Brian Katulis, a senior fellow at the Middle East Institute.

Military officials and analysts said missile and drone attacks remained the biggest retaliatory threat to U.S. bases and facilities in the region. Some also worry that the Quds Force, a shadowy arm of Iran’s military, could attack U.S. troops.

Much is at stake for Iran if it decides to retaliate. “Many of Iran’s options are the strategic equivalent of a suicide bombing,” said Karim Sadjadpour, an Iran policy expert at the Carnegie Endowment for International Peace. “They can do enormous damage to others if they mine the Strait of Hormuz, destroy regional oil facilities and rain a missile barrage against Israel, but they may not survive the blowback.”

But Iran can make it hugely expensive, and dangerous, for the U.S. Navy to have to conduct what would most likely be a weekslong mine-clearing operation in the Strait of Hormuz, according to one former naval officer who was stationed on a minesweeper in the Persian Gulf. He and other Navy officers said that clearing the strait could also put American sailors directly in harm’s way.

Mining the strait would also inflict severe economic damage in Iran because nearly all of the country’s oil exports move through the channel.

In the battle for global narratives, China has long cast the United States as a warmonger and a destabilizing power while presenting itself as a responsible global leader championing peace and fairness.

At an emergency meeting of the Security Council on Sunday, Mr. Fu said that China condemned the U.S. strikes and was joining Russia and Pakistan in drafting a U.N. resolution calling for a cease-fire, the safety of civilians and a start to peace negotiations.

The criticism of the United States was echoed in Chinese state media reports on Monday, with the official news agency, Xinhua, accusing the United States of escalating violence in the region.

“The worsening situation in the Middle East is a stark reminder that power politics and military interventions lead to nothing but chaos and instability,” the article said.

In a separate editorial on Monday, the Communist Party tabloid, the Global Times, said the U.S. strikes had weakened “the foundation of the international security order.”

On China’s heavily censored internet forums, users have left furious comments about how Iran was deceived into thinking it was negotiating a nuclear agreement with the United States, only to lower its guard and become the target of U.S. bombs.

China’s rhetoric belies a more complicated reality. Beijing has been one of Tehran’s biggest backers, diplomatically and economically. Its purchases of almost all of Iran’s oil exports have helped a brutal Iranian regime stay in power and deliver support to its terrorist proxies abroad, including Hamas, Hezbollah and the Houthis.

It remains to be seen how China might use its influence over Iran as fears of a broader conflict grow. Secretary of State Marco Rubio on Sunday urged China to persuade Tehran not to make good on a threat to close the Strait of Hormuz, one of the world’s most vital waterways for the transport of oil.

“China will certainly oppose Iran” closing the strait, said Wang Yiwei, the director of the Institute of International Affairs at Renmin University in Beijing, because of China’s need for access to Iranian oil. But it would only do so on its terms and in its own time, he suggested.

“However, it would be improper, or even counterproductive, to discuss this with the United States, or to exert pressure on Iran at the request of the United States,” he added.

When asked on Monday what China would do if Iran closed the strait, Guo Jiakun, a spokesman for the Foreign Ministry, deflected and called on the international community to “step up its efforts to promote the de-escalation of the conflict.”

The expectation that this could signify a de-escalation in the conflict was immediately evident in the energy market. The price of West Texas Intermediate, the benchmark for U.S. crude oil, dropped more than 7 percent after the Iranian strike on Qatar, to around $68 a barrel. Brent crude, the international benchmark, also fell over 7 percent.

Falling oil prices helped lift the stock market, as did further signs that the Federal Reserve could cut interest rates sooner than previously expected. Michelle W. Bowman, the Fed’s vice chair for supervision, said Monday that the central bank should consider cutting interest rates in July, becoming the second Fed official to suggest as much in recent days.

“Funny how we would have expected this to be a risk off day,” said Andrew Brenner, head of international fixed income at NatAlliance Securities. “But that trade happened in the overnight session.”

The S&P 500 index rose about 1 percent. European markets had ended trading lower.

Traders have been seeking clearer indications of whether there would be an escalation in the conflict in the Middle East — particularly any moves Iran might make that would disrupt oil shipments through the Strait of Hormuz.

A critical transit point for global oil supplies, the Strait of Hormuz last year saw about 20 million barrels of oil shipped through its waterway each day, representing about 20 percent of the world’s total supply. Most of that oil was bound for Asia.

Places like Japan and Taiwan rely on the Middle East for almost all of their crude oil imports, meaning that any disruption to traffic through the passageway could inflict a large economic blow. China is the largest buyer of Iranian oil.

Other analysts expect fallout from the conflict to be relatively short-lived. Iran’s missile attack on the American base was intercepted, leaving open a path to de-escalation.

“Stocks have a long history of eventually looking through Middle East violence (sometimes quickly), even when the U.S. gets involved,” Anthony Saglimbene, chief market strategist at Ameriprise, wrote earlier on Monday.

The oil market is also better equipped to respond to shocks than it has been in the past because of spare capacity held by exporters, according to Daniel Hynes, a senior commodity strategist at ANZ Research. Geopolitical events involving producers can have a big impact on oil markets, but in recent years prices have tended to quickly retreat as risks ease, Mr. Hynes said.

Daniel Ives, an analyst at Wedbush Securities, said there could be more volatility in stock movements this week. But, he added, the market may view the Iran threat as “now gone.” In that case, he said, “the worst is now in the rearview mirror.”