President Bush on Friday pledged $350 million to help tsunami (search) victims, and didn't rule out sending even more U.S. aid to help people recover from what he is calling an "epic disaster."

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"Our contributions will continue to be revised as the full effects of this terrible tragedy become clearer," Bush said in a statement issued in Crawford, Texas, where he is staying at his ranch. "Our thoughts and prayers are with all those affected by this epic disaster."

The pledge of $350 million is 10 times the previous $35 million U.S. assistance package that critics called miserly considering America's vast wealth. In New York, Secretary of State Colin Powell (search) also said more U.S. aid could be forthcoming.

"We had to wait and see what those needs were," Powell said. "I'm not sure $350 million is the end number. It's the number that we settled on for now."

Powell and the president's brother, Florida Gov. Jeb Bush (search), who has experience with extensive hurricane damage in Florida, leave Sunday to visit coastal areas in the Indian Ocean ravaged by last Sunday's tsunami.

The disaster, which killed more than 121,000 people and left millions homeless, hungry and thirsty, triggered an outpouring of support from across the globe.

On the second day of the crisis, America's $4 million pledge was increased to $15 million, Powell said. Three days after the tragedy, the U.S. aid was expanded to $35 million. By then many other nations had pledged millions more. France has promised $57 million, Britain $95 million, Sweden $75.5 million and Spain $68 million, although that pledge was partly in loans.

Bush spoke on the phone Friday with British Prime Minister Tony Blair, Italian Premier Silvio Berlusconi and Canadian Prime Minister Paul Martin. He said he increased U.S. assistance based on recommendations by Powell and Andrew Natsios, administrator for the U.S. Agency for International Development.

Powell said he wanted to make sure his recommendation to drastically increase the aid was based on accurate assessments of the need and not just a daily game among nations of "Can you top this?"

The money comes from the Defense Department budget and USAID's International Disaster Famine and Assistance account, said Noam Neusner, a spokesman for the White House Office of Management and Budget.

But Powell cautioned, "In due course, wherever the money comes from, those accounts will have to be replenished, and that will take action with the Congress, so we will be reaching out to Congress in the days ahead."

The United States has formed a core group with India, Japan, Canada and Australia to help coordinate relief efforts with the United Nations. Other nations were expected to join the group, led by Marc Grossman, under secretary of state for political affairs.

Powell encouraged nations to "reach deep" to make significant contributions. "The need is great and not just for immediate relief, but for long-term reconstruction, rehabilitation, family support, economic support that's going to be needed for these countries to get back up on their feet," he said after meeting with U.N. Secretary General Kofi Annan.

Annan said he was concerned that those who needed help were not getting it fast enough.

"We would want to get to everybody as quickly as we can," he said. "But the situation is very difficult, particularly in Aceh, Sumatra. We need to get access. This is one of the reasons we are talking about air capacity, we need helicopters, we need airlift."

"It is a race against time," Annan said, "and we are pressing ahead, trying to do it as fast as we can."

Bush said disaster response officials are in the region and the United States has established a support center in Thailand. More than 20 patrol and cargo aircraft have been made available to assess the disaster and deliver relief supplies, he said.

The president said the United States has dispatched the aircraft carrier USS Abraham Lincoln, a maritime squadron from Guam and an amphibious ship carrying a Marine expeditionary unit. "They will soon be in position to support relief efforts to include the generation of clean water," he said.

A congressional delegation headed by Rep. Jim Leach, R-Iowa, a former U.S. foreign service officer, is scheduled to visit Thailand and Sri Lanka next week. Senate Majority Leader Bill Frist, who often travels to blighted areas, said Friday that he will visit Sri Lanka and India next week.

The U.S. death toll has risen to 15, with eight dead in Thailand and seven in Sri Lanka. State Department spokesman Richard Boucher said some 600 Americans who were listed as missing have been found, but several thousand had still not been located.