Kofi Annan, right, with UN emergency relief director Jan Egeland

The United Nations has received $500 million in pledges of assistance for victims of the Indian Ocean tsunami. Half of the total came in one chunk from the World Bank. Secretary-General Kofi Annan expressed satisfaction with the international response, but said no amount will be enough.

Mr. Annan interrupted a winter vacation in the western United States to return to New York to head the world body's disaster relief effort.

He met Thursday with his emergency aid team, with ambassadors of affected countries and with the newly formed core group of aid donors led by the United States, Japan, India and Australia. He said he has been in close contact with Secretary of State Colin Powell to coordinate relief efforts.

"I spoke to Secretary of State Powell yesterday, as the announcement was made, and we've also spoken this morning," he said. "The core group will support the U.N. effort. We expect the core group to grow. There are other countries that have indicated a desire to join the core group, and it will be a good thing that we will have a real international effort, and it is clear that their purpose is to work with us and support the U.N. effort, and we're going to make it a truly international effort."

View of village destroyed by tidal waves at Kolachal, in southern Indian state of Tamil Nadu

Mr. Annan described the Indian Ocean tsunami as an unprecedented global catastrophe that requires an unprecedented global response. But he said the initial outpouring of assistance pledges had been very good.

"A total of half-a-billion dollars in assistance has been pledged or received, as well as contributions in kind," he said. " More than 30 countries have stepped forward to help, as have millions of individuals from around the world."

Mr. Annan said half the money pledged, $250 million, came in one donation from the World Bank.

The secretary-general and U.N. emergency relief director, Jan Egeland, outlined a massive aid distribution plan using the Thai capital, Bangkok, as its hub for moving goods to the worst-hit areas.

Member of International Committee of the Red Cross, ICRC, loads relief aid for victims in Asia onto Antonov 12 cargo plane, Thursday

He commended the work of local Red Cross and Red Crescent Societies in providing immediate assistance, but admitted that, even with all the aid being offered, the international community's resources would be stretched thin. He admitted that the scope of the disaster is so large, everything that can be done may still not be enough.

"That is possible, because the needs are enormous," Mr. Annan noted. "And it is conceivable that one may not be able to fulfill every possible need of each of the countries and each of the coastal villages that have been destroyed. But we cannot forgive ourselves for not even trying, not even really making an effort to help people meet their desperate needs. Our common humanity demands it."

U.N. officials say a wider appeal for assistance is to be launched within a week, in hopes of raising several hundred million more dollars. That money would be intended to provide emergency aid over the next six months. A third appeal for several billion dollars is expected later, to finance reconstruction efforts.