See high-definition photos of the Pakistan flooding.
(CNN) -- The death toll from massive floods in Pakistan rose to 1,497 on Friday as U.N. chief Ban Ki-moon said the crisis is a "slow-motion tsunami" that is expected to grow.
The number of homeless as a result of flooding has doubled to 4 million.
Ban urged the international community to give more aid during a special fundraising meeting Thursday night.
"Make no mistake," he said. "This is a global disaster, a global challenge. It is one of the greatest tests of global solidarity in our times."
Video: Life in a flood relief camp
Video: Aid slow to flood-ravaged Pakistan
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Video: U.S. ramps up aid to Pakistan
The U.N. secretary-general, who traveled to Pakistan last weekend to visit sites devastated by the disaster, said almost 20 million people need shelter, food and emergency care.
"That is more than the entire population hit by the Indian Ocean tsunami, the Kashmir earthquake, Cyclone Nargis, and the earthquake in Haiti -- combined," he said.
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The United Nations has already appealed for $460 million over the next three months, Ban said, and although donors delivered more than a half, the available resources are not sufficient to meet the needs on the ground.
The European Commission has pledged 40 million euros ($51 million) since July 31 for the flood victims. It said it will mobilize an additional 30 million euros (about $38 million).
"This disaster is like few the world has ever seen. It requires a response to match," Ban said. "Pakistan needs a flood of support."
Secretary of State Hillary Clinton, who also attended the General Assembly meeting, announced an additional $60 million in U.S. aid. The funds bring to $150 million the amount pledged to Pakistan by the United States.
"I want the people of Pakistan to know: The United States will be with you through this crisis," she said. "We will be with you as the rivers rise and fall. We will be with you as you replant your fields and repair your roads. And we will be with you as you meet the long-term challenge to build a stronger nation and a better future for your families."
Clinton urged other nations to help the nation meet its funding goals.
Analysts have blamed "donor fatigue" for the delay in aid.
Pakistan has been on a seemingly constant round of donor needs -- to revive its feeble economy, to fight the Taliban and to recover from the 2005 Kashmir earthquake and the 2009 refugee crisis.
