Former US President Bill Clinton has called for the co-ordination of relief efforts in response to the Asian quake, as aid starts to flood into the region.
Aid must be co-ordinated, says Clinton
"It is really important that somebody takes the lead in this," he told the BBC's Today programme on Tuesday.
The UN has already begun a huge relief effort to help the 11 nations affected.
A UN aid appeal and possibly a donor summit is planned for the New Year, although individual nations are already sending their own donations.
"People are generous... the challenge is to make sure the right aid goes to the right place," Arjun Katoch, a UN relief co-ordinator in Geneva told BBC News.
Millions of people are homeless as a result of the tremor and sea surges, and the disaster zone is now threatened with outbreaks of disease.
Entire settlements need rebuilding
About 40,000 people have been killed and many others are still missing.
A plane chartered by the UK charity Oxfam is carrying 27 tonnes of water tanks, pumps and taps to Sri Lanka and Indonesia, to set up emergency drinking water systems and latrines.
The US aid organisation Care said it was already distributing food to 14,000 Sri Lankans and that it was preparing a "major operation".
Japan had pledged to provide around $30m (£15.5) in aid and is sending its navy to help rescue survivors off Thailand's coast.
Japan's foreign ministry also said doctors would be sent to Sri Lanka and a damage survey team to
The United States has promised $15m in immediate aid and has said more will follow. The European Union has pledged $40.5m.
The UK has given £400,000 ($773,000) through the EU to a Red Cross appeal and is providing about £50,000 ($96,000) to the World Health Organization.
China announced that it was giving $2.6m in aid, in the form of food,
tents, blankets and cash.
India is sending emergency supplies to Sri Lanka and the Maldives. France has dispatched 100 doctors, who are travelling to the area with Foreign Minister Michel Barnier.
Australia is giving an initial $7.8m while Singapore is sending $1.2m.
People in affected countries are also taking it upon themselves to raise money.
Sri Lankans living in the US and the UK are gathering funds for victims in their home country, which was among worst hit.