Former US presidents Bill Clinton and George Bush Sr are touring Asia's tsunami killing fields from today in an effort to prevent donor fatigue and highlight the enormous amount of rebuilding left to do.

Appointed by the current president to lead US fund-raising for survivors of the December 26 tsunami, the pair plan a lightning four-nation tour to keep world attention on the disaster and encourage Americans and US firms to keep giving.

"The two former presidents were appointed for funding purposes to coalesce the private sector of the US to help the tsunami victims," US embassy spokesman Kathleen Boyle said in Phuket, the Thai resort island where the trip begins.

"The public profile (of the disaster) is indeed part of the purpose of this trip," she added.

Private donors worldwide are estimated to have given over $2 billion so far in relief aid for the world's worst natural disaster in living memory, which is feared to have killed 300,000 people around the Indian Ocean's rim.

A lot of that money has been channelled via the internet , which emerged during the crisis as a prodigious source of private relief funds. But Mr Clinton told the recent Davos leaders' summit that donor fatigue was now a major challenge.

To keep the computer mice clicking, the trip will also try to highlight how the millions have already been spent, Mr Boyle said, adding that Mr Clinton and Mr Bush would start their trip with a visit to a Thai fishing village under reconstruction.

The village of Ban Namkhem was wiped out when a wall of water smashed into the palm-fringed coast of southwest Thailand, turning stretches of beach from a picture postcard to a gruesome wasteland littered with bodies.