Donald Trump fired back Tuesday at President Barack Obama, saying in an interview that he knows “more about foreign policy” than the current commander in chief.

“He talks about Ukraine. I believe I know far more about foreign policy than he knows,” Trump said to Fox News host Bill O’Reilly on "The O'Reilly Factor." “He talks about Ukraine, how tough he is, how tough he is with Russia. In the meantime, they took over Crimea and I understood that.”

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Trump also said Obama is the “worst president maybe in the history of our country." Obama said earlier in the day that Trump is “woefully unprepared” for the job of president.

The Republican nominee also hit Obama for his relationship with Russia, advocating for working with the superpower to fight terrorism.

“Wouldn’t it be a wonderful thing, frankly, if we actually got along with Russia and worked out some kind of a deal where we go and knock the hell out of ISIS along with NATO and along with countries that are in the area,” Trump said. “Wouldn’t that be wonderful, as opposed to fighting?”

Trump, who has weathered accusations that he is cozy with Russia and strongman Vladimir Putin, previously said that World War III would break out if the United States was to intervene to help Ukraine take back Crimea.