Food, medicine, clothing and other desperately needed items have started to arrive in countries hardest hit by the devastating earthquake and tidal wave, and the United Nations (search) says tens of millions of dollars have been pledged to help survivors.

But billions of dollars will be needed to repair the damage in countries from southeast Asia to the Horn of Africa, said Undersecretary-General for Humanitarian Affairs Jan Egeland, who is also the U.N. emergency relief coordinator.

"A very, very major — perhaps one of the most devastating natural disasters ever — is confirmed," he told reporters Tuesday.

"Millions and millions of people are affected. They have had their water supplies destroyed, they have lost their livelihoods, homes, and many of them have lost relatives."

So far, he said, pledges of assistance for the emergency relief effort have reached tens of millions of dollars.

"The international assistance has been immediate and generous," Egeland said. "The U.S. at $15 million is one of the most generous pledges so far. It is exactly what we need to get started ... but we will need very substantive pledges."

"The damage will be in the billions of dollars," he said.

The United Nations has sent disaster assessment teams to the affected countries and relief organizations are distributing supplies. The global body is also starting to put together an appeal for international aid.

Worst-hit have been Indonesia, Sri Lanka, India, Thailand and the Maldives. But Malaysia, Myanmar, Bangladesh, Somalia, Tanzania, Seychelles and Kenya have also reported deaths from the tidal wave that sped across the Indian ocean Sunday morning.

"I have made big appeals in the past but this is unprecedented because very many countries are involved," Egeland said.

In Geneva, U.N. officials met Tuesday with governments, donors and aid organizations. On the same day U.N. ambassadors from some of the worst affected countries met Egeland in New York to discuss the disaster.

Sri Lanka's U.N. Ambassador Bernard Goonetilleke said the country's fishing and tourism industries — two mainstays of the economy — have been "practically devastated as a result of the tidal wave." He said his country desperately needed food, medicine and water purification tablets.

The Rome-based U.N. World Food Program (search) said it has begun distributing food in Sri Lanka. Twelve truckloads were headed to the country's southern and eastern coasts, carrying about 185 tons of food, including rice, lentils and sugar, spokeswoman Caroline Hurford said. UNICEF (search) has already provided more than 30,000 blankets, as well as sleeping mats and clothing.

The International Committee of the Red Cross (search) has sent medical supplies for about 120,000 people to the country to provide basic care and treat possible cases of diarrhea.

Mohamed Latheef, the Maldives' ambassador to the United Nations and the United States, said 130 of the country's 200 islands were substantially affected, 14 islands had to be evacuated and 19 inhabited islands have not been heard from. "Quite a few are under water," he said.

The U.N. Office for the Coordination of Humanitarian Affairs, known as OCHA, said it was organizing an airlift of 15 tons of relief good including tents, water containers, plastic sheeting, and emergency health kits, that was being paid for by the Norwegian government.

Indonesia's economic counselor Prayono Atiyanto said his country urgently needs food, body bags, fresh water, generators, medical supplies, blankets, mosquito nets, water buckets, clothing and beds, while Thailand's U.N. Ambassador Laxanachantorn Laohaphan said the government's "wish list" includes forensic experts, body bags and a refrigerated mortuary.