Defending the United States against criticism that it was "stingy" with its humanitarian aid, Secretary of State Colin Powell (search) said Tuesday America "will do more" to help the victims of the tragic tsunamis in Asia and Africa.

"It will take time to see what the needs of these nations are and how best to help them," Powell said Tuesday on FOX. "This is an unprecedented catastrophe."

Initially, the U.S. government pledged $15 million and dispatched disaster specialists to help the Asian nations devastated by the catastrophe. Tens of thousands of people have been killed in the tsunamis and earthquake in parts of India, Sri Lanka, Indonesia, Malaysia, the Maldives and other countries.

The government said it would give $4 million at first to the Red Cross (search) and related organizations and another $10 million to other disaster relief groups.

On Monday, President Bush had already sent letters of condolence to several different countries affected by the disaster.

But Jan Egeland (search), the U.N. humanitarian aid chief, has accused America of being cheap with its funding for the catastrophe.

"It is beyond me why we are so stingy, really," Egeland said at a Monday press conference.

Powell made the morning news show rounds Tuesday and said that he regretted Egeland's statements.

"The United States has given more aid in the last four years than any other nation or combination of nations in the world," Powell told the Associated Press. "This is indeed an international tragedy, and we are going to do everything we can."

The secretary said that at least 11 Americans have died in the disaster and "hundreds" are unaccounted for.

Still, Egeland said America should do more.

"We were more generous when we were less rich," Egeland told reporters Monday. "Even Christmastime should remind many Western countries at least how rich we have become."

Powell explained Tuesday on FOX News that different countries impacted by the tragedy had different needs according to their economic situations and governments.

"Some are better able to manage the problem without outside assistance, and other nations are not as equipped to deal with the problem," he told FOX Tuesday. "They will need more assistance.

"Sri Lanka, for example, will need a lot more help than India, which is a more sophisticated nation, able to manage a great deal of its own relief effort," Powell said.

Powell made condolence telephone calls and offered American assistance to the foreign ministers of Thailand, the Maldives, Sri Lanka, India, Indonesia and Malaysia.

From his ranch in Crawford, Texas, on Monday, Bush sent letters of condolence to the leaders of the seven countries wracked by the disaster.

"This is a terrible tragedy," White House spokesman Trent Duffy said. "There is a significant loss of life. And our thoughts and prayers are with all those who are suffering."

American ambassadors released $100,000 each to India, Indonesia, the Maldives and Sri Lanka.

Supplies of shelter, food and water cans on reserve in the Philippines and Dubai will also be distributed, according to Ed Fox, assistant administrator of the U.S. Agency for International Development (search).

Millions of people who were driven from their homes or hotels will need shelter, food and clothing, he added. The initial $15 million U.S. contribution was issued while surveys were conducted, Fox said.

The Australian government pledged about $7.6 million in immediate aid.

A spokesman at U.S. Pacific Command in Hawaii said Monday that in addition to three Navy P-3 Orion surveillance planes sent to Thailand, the military also is loading five or six Air Force C-130 cargo planes with tents, clothing, food and other humanitarian items for delivery to Thailand.

Pacific Command spokesman Lt. Col. William Bigelow (search) said he wasn't authorized to identify the three countries, but other government officials said they were Sri Lanka, Indonesia and Thailand.

Pacific Command also is assembling small assessment teams that will be dispatched to three countries in the region to assess how U.S. military resources can best be applied in those countries.

The U.S. Navy said it sent three P-3 surveillance aircraft from Kadena air base on the Japanese island of Okinawa to Utaphao, Thailand, to conduct survey operations, and possibly help with search-and-rescue efforts.

The Navy said it had no reports of damage to any of its ships or bases in the region.

And James D. Wolfensohn, president of the World Bank (search), said bank teams were discussing potential assistance with the governments of the countries that suffered losses.

On Sunday, the managing director of the International Monetary Fund, Rodrigo de Rato, said the Fund "stands ready to do its part to assist these nations with appropriate support in their time of need."

Powell encouraged donations, and suggested checking the State Department Web site for ways to help.

"We have to make sure we send people what they really need and not just flood them with things they don't need," said Powell.

FOX News' Catherine Donaldson-Evans, Mike Emmanuel and The Associated Press contributed to this report.