The UN has launched a special meeting of the General Assembly to try to boost the international aid commitment to flood-stricken Pakistan.
Secretary General Ban Ki-moon told the session the floods were like "a slow-motion tsunami" that presented an ongoing crisis.
The UN says it has raised nearly half the $460m (£295m) wanted for initial relief but the response remains slow.
Large parts of the country remain submerged after weeks of heavy rain.
There are fears of more flooding as water continues to surge south down the Indus River.
At least 1,500 people have died in the floods, which have destroyed roads and bridges, flooded farmland and knocked out power stations.
More than four million people have no shelter, and millions more need immediate assistance, the UN says, yet only about half the $460m (£295m) wanted for initial relief has been committed.
Pakistani officials say 20 million people have been affected by the disaster. Tens of thousands of villages remain underwater.
After a slow start, more pledges of donations from the international community have come in but Mr Ban said the crisis was far from over.
"The rains could continue for weeks. And only now are we beginning to understand the true scope of this disaster.
"Excellencies, ladies and gentlemen, Pakistan is facing a slow-motion tsunami. Its destructive power can accumulate and grow with time," he said.
He called the flooding a "global disaster" that was "one of the greatest tests of global solidarity".
Hour of need
The BBC's Kim Ghattas at the UN says the resolution will not produce any concrete action plan but is a sign of how nervous the US and the UN are about the level of international assistance given to Pakistan so far.
The session is a clear attempt to build a sense of urgency about a natural disaster that will have a lasting impact on a country that is key to the fight against the Taliban and al-Qaeda, says our correspondent.
Pakistan's Foreign Minister Shah Mehmood Qureshi warned that a failure to help his country in its hour of need could be exploited by extremists.
"If we fail, it could undermine the hard-won gains made by the government in our difficult and painful war against terrorism. We cannot allow this catastrophe to become an opportunity for the terrorists."
Urging greater action from the international community, US Secretary of State Hillary Clinton announced a $60m increase in American aid to $150m.
"We know we face a humanitarian disaster of monumental proportions... And here at the United Nations, we often speak of a desire to forge a more humane fellowship with humankind. And today we must match that aspiration with action."
After three weeks of heavy rains, some 4.6 million people are without shelter, UN spokesman Maurizio Giuliano said on Thursday. Most of them are in the provinces of Punjab and Sindh.
Some of them would be able to return to the homes they were forced to leave, he said, but many would have to rebuild houses destroyed by the force of the floods.
Officials and aid agencies in Pakistan say there are signs that the crisis is still deepening, as new flood waters continue to surge south along the Indus river and more flood defences collapse, forcing people to flee their homes.
There are growing concerns for those surviving without proper shelter, food or clean drinking water and fears there could be a second waves of death from water-borne disease.