U.N. Secretary General Kofi Annan urged nations to immediately come forward with the billions in aid they've promised, amid warnings that another 150,000 people may die from disease - more than doubling the confirmed toll of 140,000.
While, the United Nations has warned some of the promises might not be honored - as happened in previous disasters.
As the conference ended, world leaders issued a declaration pledging to work together and set up a tsunami warning system to ensure that next time such a wave is generated, coastal communities will have time to flee to higher ground.
"This unprecedented devastation needs unprecedented global response in assisting the national governments to cope with such disaster," the declaration said.
could take up to a decade, the leaders said.
Powell told conference leaders Thursday that the U.S. - the fourth largest donor, behind Australia, Germany, and Japan - might wind up increasing the amount of its pledge.
The U.S. has pledged $350 million in direct financial aid to the relief effort, and is spending uncounted millions more to run a large military supply and relief mission using U.S. ships, planes and helicopters.
"We know full well that as the true dimension of this tragedy continues to emerge it may be necessary for us to make a larger contribution," said Powell.
The European Union announced Thursday that it will donate $132 million for immediate tsunami relief and additionally will consider setting up a euro1 billion loan for affected nations.
European Union Commission president Jose Manuel Barroso said he will ask the European Parliament to approve another $461 million in aid for longer term reconstruction of countries devastated by the.
"I think the European Parliament is ready to be very generous," said Barroso, adding the loan would be on "very favorable terms" and administered by the European Development Bank and other international banks.
Another European official warned against getting caught up in comparisons between nations.
"It's not important to make a competition to know who will promise the highest level of amounts," said Louis Michel, European Commissioner for Development and Humanitarian Assistance. "It's important to see who is ready to pay completely."
Powell says tsunami relief efforts by the United States, India, Japan and Australia - a core group formed to coordinate their initial response - will now be merged into U.N.-led operations.
"The core group helped to catalyze the international response. Now having served its purpose, it will fold itself into the broader coordination efforts of the United Nations," Powell said in remarks presented at the summit.
Annan urged nations to channel $1.7 billion of the funds to the United Nations for relief, including $977 million for emergency aid.
"Whole communities have disappeared," Annan said. "Millions in Asia, Africa, and even in faraway countries, are suffering unimaginable trauma and psychological wounds that will take a long time to heal. Families have been torn apart.
"The disaster was so brutal, so quick, and so far-reaching, that we are still struggling to comprehend it," Annan added, stressing the need for donor "pledges to be converted into cash quickly ... It is a race against time."
The U.N. chief said the number killed across Asia and Africa will likely exceed 150,000, but the exact figure would never be known. The World Health Organization warned the toll could double if aid doesn't reach survivors soon.
"As many as 150,000 people are at extreme risk if ain the affected areas occurs," said WHO Director-General Dr. Lee Jong-wook.
The Jakarta summit leaders agreed that a tsunami warning system like the one already in place in the Pacific should be set up in the Indian Ocean as quickly as possible.
Japan plans to offer technical expertise to set up the warning system. The country has one of the world's most advanced networks of fiber-optic sensors, which can warn of deadly tsunami within two minutes of a quake.
"No longer must we leave ourselves so vulnerable and so exposed," Thai Foreign Minister Surakiart Sathirathaim said. "It is well-proven that 10 minutes advance warning can save hundreds of lives."
Countries around the world have pledged about $4 billion in addition to sending troops and teams of medics to the stricken regions. But there were fears much of the pledged money would not materialize.
Just over a year ago, donors promised Iran more than $1 billion in relief after an earthquake killed 26,000 people there. Iranian officials say only $17.5 million has been sent.
In a final defiant paragraph to their declaration, the leaders vowed to work together to rebuild.
"We believe that through concerted efforts, spurred by spirit of compassion and sacrifice and endurance, together we will prevail in overcoming this catastrophe," the statement said.