US President Barack Obama has declared one of the biggest relief efforts in America's history to help Haiti's earthquake victims.
Mr Obama has met two of his predecessors in the White House to seek their support.
Former presidents George W Bush and Bill Clinton will lead US fundraising efforts through the Bush-Clinton Haiti Fund.
Mr Bush on Saturday urged Americans to send "cash" and Mr Clinton said Haitians "can escape their history and build a better future if we do our part".
Mr Obama warned that recovery would take a long time.
Meanwhile, a United Nations agency says the Haiti earthquake is the worst disaster it's ever confronted.
The UN Office for the Co-ordination of Humanitarian Affairs in Geneva says the country has been "decapitated".
It says the situation is worse than the devastation wrought by the 2004 tsunami in the Aceh province of Indonesia.
Haiti's capital Port-au-Prince was extensively damaged by a magnitude 7.0 earthquake on Tuesday.
The UN meanwhile confirmed the head of its mission in Haiti has been found dead in the rubble of its collapsed HQ.
Xinhua news agency reports that the body of Hedi Annabi, of Tunisia, was recovered at 1422 (2022 GMT) on Saturday.
The death of his deputy, Luiz Carlos da Costa of Brazil, has also been confirmed, as well as the death of acting police commissioner, Doug Coates of Canada.
Clinton to meet President & PM
US Secretary of State Hillary Clinton arrived in Haiti on Saturday. She was to meet President Rene Preval and Prime Minister Jean-Max Bellerive at the airport in an effort to co-ordinate the relief effort.
Mr Preval has been living and working in the judicial police headquarters, not far from the airport, since the presidential palace was destroyed on Tuesday.
Mrs Clinton says food, water, medicine and restoring communications are the priority.
According to Haitian Interior Minister Paul Antoine Bien-Aime, 50,000 bodies have been collected, but the total number of dead could be "between 100,000 - 200,000".
The United Nations says about 300,000 people are homeless.
Thousands of people are reported to be leaving the capital to find food, water and shelter in the countryside, away from aftershocks and looting.
The UN has launched an appeal for $US562 million. A total of about $US360 million has been pledged so far for relief.