UN peacekeepers have begun taking over from a US-led multi-national force in flood-devastated Haiti.
The US-led force handed over the mission to UN peacekeepers
Brazilian troops are leading the force of 8,000 UN soldiers and civilian police, although it is likely to be a month before they are all in place.
The troops will be responsible for ensuring security and maintaining the country's fragile peace.
But helping flood survivors will be the immediate task. A BBC correspondent there says they face a daunting role.
At least 2,000 people are known to have died or disappeared after severe flooding over the past week.
The UN peacekeepers will replace a multi-national force sent to Haiti to maintain security after former President Jean-Bertrand Aristide left in February.
At a symbolic ceremony in the capital Port-au-Prince, US Marine General Ronald Coleman handed the baton to a Brazilian army general, Augusto Heleno Ribeiro Pereira.
Haitians are expecting the new force, which is eventually to comprise 6,700 military officials and 1,622 civilian police officers drawn from 14 nations, to help the thousands of flood survivors in the east of the country who still depend on aid to survive.
With access routes and roads flooded, aid agencies have been struggling to reach survivors in remote areas with airlifts, using helicopters belonging to US and French troops.
And although over the past few days peacekeepers have been overseeing the delivery of dozens of jeeps and lorries, no helicopters are expected in the UN equipment.
Relief workers say there is a growing danger of disease, with more rains expected in June, the usual wet season.
The International Committee of the Red Cross says it is worried that dams formed by debris above the villages of Bawa, St Michel, Nan Galette and Naroche could burst if there is more heavy rainfall.
"Our biggest concern right now is that these four villages are at risk of landslides, mudslides and rockslides," spokesman Bernard Barratt told BBC News Online.
"We've distributed plastic sheeting for people to make temporary shelters in hilly areas and we're trying to get local civil defence people to keep watch at night," he said.
More than 100 tons of food alone has been airlifted to the survivors, but military helicopter airlifts have been suspended for a day for maintenance.
The military fears that now some of those not directly affected by the floods are travelling to the area hoping to receive the handouts.
"We are concerned that people who are outside the immediate vicinity are now coming in to possibly take advantage of the fact that food is being distributed," said Colonel David Lapan, a spokesman for the outgoing force.
The Haitian prime minister, Gerard Latortue, has said he expects the UN force to disarm an estimated 16,000 militants who pitched the country into near-total anarchy.
The troops will also be responsible for training the local police force and working on development projects in a country which has seen more than 30 coups in 200 years.