The reasons are complex, but the officials say the slow evolution of the crisis and the seasonal nature of Pakistan floods have slowed responses to the crisis, which has left some 4 million people homeless and already killed at least 1,500 in what the United Nations reported is the worst flooding there in memory.
And it doesn't help that the crisis comes as the industrial world struggles to shake off a deep international recession.
U.S. Ambassador Richard Holbrooke, special envoy to Pakistan and Afghanistan, told ABC's "Good Morning America" today that beyond the humanitarian crisis are fears that Islamic militant groups could make inroads by filling the void left by the slow international response.
"We are not oblivious to the political and security implications of this," Holbrooke said. "Pakistan is not just another country that has been hammered by a tragedy; it is at the epicenter of global terrorism."
Relief experts say public response has been slow partly because of the lack of drama that surrounded the start of the flooding, which began with the onset of monsoon rains last month and now has spread to cover a vast swath of the impoverished nation.
"It's like all of Florida being underwater, or all of the cropland in Iowa," said Kate Conradt, spokeswoman for Save the Children. Her organization set a target of $15 million in donations, yet has drawn only half that.
"It's not a massive earthquake like Haiti that just pulverized a city," she said. "There has been way less media coverage of this disaster, so the donating public doesn't know how bad it is. They're just now starting to pick up concern and a deeper understanding of what's happening."
At the International Rescue Committee, Asia regional director Mike Young said individual donations have also been slow in coming, though in recent days governmental and institutional giving have picked up.
"In terms of private contributions coming in through the website and places like that, it's not to the scale that we have witnessed in other disasters," he said, putting total donations at $10 million, including institutions. He was unable to break out a total for individual donors.
He said the organization noticed a similarly weak donor response when some 100,000 Pakistanis were displaced last year as the Pakistani military moved against Islamic insurgents.
"We can't pin down a cause, but this huge disaster comes on the heels of another huge disaster in Haiti," Young said, suggesting donor fatigue might be playing a role. "And how the disaster developed was very slow, taking weeks, not like an earthquake. And the mortality rate is low," compared with a sudden disaster like a quake or landslides.
Yet the death tally is expected to rise in the weeks ahead as water recedes and contaminated drinking water and standing pools help spread disease, he said.
"We've already seen the first cases of cholera," Young said. "Being able to mobilize money as quickly as possible and translate that into aid on the ground is important in heading off that second crisis."
There are several places collecting contributions. Network for Good (AOL is a founding partner) is acting as a clearinghouse for donations. But individual programs are accepting money directly through their own sites, including these organizations:
American Red Cross
CARE
International Rescue Committee
Oxfam America
Save the Children