Secretary of State Colin Powell said Thursday the United States is taking a wait-and-see attitude before pledging more cash to tsunami (search) relief, but is helping in other ways such as easing restrictions on military cooperation with Indonesia (search).

"I think it's prudent to be careful with respect to these numbers," Powell said at a news conference following an international summit on relief coordination. "These are not insignificant numbers."

At the meeting, he announced that the U.S.-led group of countries that organized initial relief operations will turn its work over to the United Nations (search).

President Bush had set up the initial relief organization outside the world body. The Bush administration is sometimes suspicious of the U.N. bureaucracy, but had insisted that the separate group of nations was not at odds with the United Nations.

The United States will retain control of relief flights by its military at a special command center set up in Thailand.

The United States has pledged $350 million in government 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," Powell said at the relief summit. He gave no specifics and no firmer timeline.

The United States took early criticism for being slow to commit cash and political muscle to the relief effort, but Powell and other U.S. officials say Washington upped its commitment appropriately, as the scope of the damage became clearer. It is fourth behind Australia, Japan and Germany in aid pledged.

"I think $350 million was more than generous," Powell said at the news conference.

Global pledges now near $4 billion.

Massive relief needs in the devastated Aceh region outweigh concern that the Indonesian military might use American armament against its own people, Powell said at the news conference, so the United States should help get sidelined Indonesian C-130 cargo planes flying again.

"It seems to me the humanitarian need you saw yesterday trumps reservations we have," Powell said. He was referring to a helicopter flight he took Wednesday over Aceh's destroyed northwestern coast.

Most U.S. sales of military gear have been halted since 1999, when Indonesian soldiers were accused of human rights violations in separatist East Timor. The government is also fighting separatist rebels in Aceh, the region hardest-hit by the Dec. 26 tsunami.

The United States plans to allow spare parts for C-130s to go to Indonesia now, which Powell said could get five more planes flying in Aceh. Out of a fleet of 24 Indonesian C-130s, only seven are usable now, he said.

C-130s are not combat planes, but Indonesian pilots may have recently used them to attack rebels.

Indonesia is anxious to end the military restrictions, and Powell said that gives the United States leverage to dissuade the Indonesians from using the repaired planes "in a way not intended," such as attacking the rebels.

American C-130s, along with some from Australia and other countries, are already flying in Aceh.

Powell has nearly finished a three-nation tour of hard-hit countries that began in Thailand and included a visit Wednesday to the devastated coastal regions of Sumatra, in Indonesia. Tens of thousands died there, and whole villages were inundated. He will visit Sri Lanka on Friday.

"On our return to Washington, we will report directly to President Bush regarding the horrors people in this region have endured," Powell said.