President Bush said Monday the United States has a duty to continue helping victims of the Indian Ocean tsunami (search), but he did not put any more money behind his commitment for long-term assistance.

After hearing Secretary of State Colin Powell's firsthand report of damage in the region, Bush told reporters "we'll see" if the United States will give more than the $350 million in relief already pledged.

Bush said the United States wants to make sure its contributions are being used to provide necessary relief and then work with the United Nations (search) and other nations to assess ongoing needs in the region. "The dollars are demand-driven," he said.

"The government of the United States is committed to helping the people who suffer," Bush said. "We're committed today, and we will be committed tomorrow."

After the briefing from Powell, Bush headed to the U.S. Agency for International Development (search) headquarters to speak with employees and other leaders of about two dozen charities, several with religious affiliations, that are providing humanitarian assistance. Bush thanked both the government and private workers for the help they are providing in the recovery.

"This is one of these projects that's not going to happen overnight," Bush told aid workers. "The intense scrutiny may dissipate, and probably will, but our focus has got to stay on this part of the world. We have a duty. We have made a commitment, and our commitment is a long-term commitment, to help these good folks in the part of the world that got affected get back on their feet."

Bush also asked Americans to continue making contributions to private groups for the relief effort, but pleaded with donors not to simultaneously reduce money they would give to those organizations for other purposes.

That plea came despite questions about where the U.S. government money going to the relief effort is coming from and whether U.S. humanitarian assistance would be reduced elsewhere to pay for it.

Earlier Monday, White House press secretary Scott McClellan said the tsunami-ravaged nations will need much more help than the assistance already pledged by the rest of the world and that the United States "will be there throughout to help the people of the region recover."

But Bush did not promise that the U.S. commitment of $350 million in aid would rise. "It could," he said, when asked.

Bush also got an update on government efforts to expand the tsunami warning system so it covers both coasts of the United States and countries around the world.

Most of the countries that were hit hardest by the Indian Ocean tsunami do not participate in the warning system. People there had no notice of the approaching waves. The United States has a system for the Pacific Ocean but none for the Atlantic Ocean, where the chance of an earthquake is almost nonexistent.

Any money the United States spends to expand the system would not come out of the $350 million in disaster aid, but through other spending.

McClellan said only $78 million of the $350 million that was pledged has already been spent.

Bush said the biggest demand is in the Banda Aceh (search) region, which Powell visited during his tour of Indonesia, Thailand and Sri Lanka. "I think Colin referred to Banda Aceh as something the equivalent of Hiroshima," Bush said.

McClellan said Powell gave Bush a detailed report of the devastation in Banda Aceh, including showing him pictures of the debris and bodies of the dead.