The United States upped its initial disaster relief pledge for the victims of the tsunami in Asia and Africa by $20 million as Secretary of State Colin Powell (search) defended the U.S. against criticism it was "stingy" with aid.

State Department spokesman Adam Ereli told FOX News that the United States viewed helping the disaster victims as a long-term commitment, adding that Washington was preparing for "a long and difficult period of assessment and then relief and reconstruction."

The amount of aid coming from the U.S. Agency for International Development (search) was expected to increase by the millions, and State Department officials stressed that the $35 million donation was "preliminary."

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

At least 12 Americans were killed in the disaster and "hundreds" were unaccounted for, Powell said.

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 tsunami (search) and earthquake in parts of India, Sri Lanka, Indonesia, Malaysia, the Maldives and other countries.

A USAID official told FOX News on Tuesday that the amount was increased to $35 million following a meeting between Powell, Deputy Secretary of State Richard Armitage and USAID administrator Andrew Natsios. The additional funds were approved later that day.

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 News. "They will need more assistance."

Jan Egeland (search ), the U.N. humanitarian aid chief, on Tuesday stepped back from criticisms he made of wealthy nations following Sunday's earthquake and tsunami.

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

The White House did not strike back, instead suggesting that Egeland's statement may have been misinterpreted.

Egeland insisted on Tuesday his comments had been taken out of context, and in a press statement called the response from countries including the United States "immediate and generous."

The U.N. said that there was no intended criticism of Washington. "We just wanted to make the case that rich countries can always do more," a spokesman said.

The spokesman also acknowledged that the United States contributes about half a billion dollars a year to U.N. humanitarian programs — more than any other country. In the statement, Egeland said Washington's initial pledge of $15 million was "exactly what we need."

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."

While not all of the $15 million in U.S. aid approved on Monday had been totally disbursed to Asia, Ereli said that at least $5 million had already been spent on food, water purification equipment, blankets and shelter materials.

On Monday, Egeland urged nations against holding back on spending,

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

U.S. Reaches Out

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

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," Powell said.

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