"We are dealing with vast areas," said John Ohiorhenuan of the U.N. Capital Development Fund. "Most of that access will have to be by helicopters."
U.S. aid groups are working feverishly to raise money. The humanitarian group Direct Relief International will send urgently needed medicines donated by pharmaceutical companies.
Some offers of help are on a much smaller scale. Across the United States, Sri Lankan immigrants are collecting what they can to send home.
"It's so awful -- anything to help," said Rizwan Mowlana, executive director of the Maryland chapter of the Council on American-Islamic Relations, who lost 30 relatives in the disaster.
Relief agencies are asking Americans not to send clothes or shoes, which are produced in places like India and Thailand. Buying those items locally will help the region's economy. Aid groups say Americans should give one thing -- money.
List of Aid Agencies Accepting Contributions for Tsunami Disaster
ABC News' Linda Douglass filed this report for "World News Tonight."
