UN Secretary-General Kofi Annan is cutting short his end-of-year holidays to return to the UN headquarters in New York Wednesday night to oversee the world body's relief efforts after the devastating tsunami that struck southern Asia.

He will meet Thursday morning with UN Emergency Relief Coordinator Jan Egeland and the heads of other UN agencies involved in the relief effort, which officials have called unprecedented and possibly the largest ever launched by the world body, UN spokesman Fred Eckhard said.

Over the past two days, Annan has spoken to leaders of the nearly one dozen countries hit by the disaster to see what they need most urgently and has also been in touch with leaders of major donor nations to review the international relief effort and to underscore the UN's coordinating role, the spokesman said.

Earlier Wednesday Annan discussed the situation with US Secretary of State Colin Powell.

The latest estimated death toll from Sunday's earthquake and tsunami has topped 76,000, with millions more affected.

In an interview on CNN Tuesday night, Annan called for a generous response to the aid appeal the UN will launch on Jan. 6, warning that the emergency relief phase for the catastrophe together with the recovery and the reconstruction phase will require billions of dollars.

"The needs are enormous. They need food. They need clean water.They need shelter. They need medication," he said. "We need to begin worrying immediately about the non-food items, sanitation, clean water, to ensure that epidemics do not set in. And so they need lots of help and are looking to the international community to respond and respond generously."