A US military helicopter delivered troops from the 82nd Airborne Division Tuesday to the centre of Port- au-Prince, where they secured l'Hopital General, the capital city's main hospital near the presidential palace.
The hospital had asked for protection so it could continue caring for the massive numbers of earthquake victims, Lieutenant Ryan Smedile told the German Press Agency dpa.
Uninjured Haitians seeking food, water and shelter had been threatening to interrupt the work of the doctors and nurses.
The 82nd Airborne based in Fort Bragg, North Carolina, arrived two days before, and had been patrolling the streets in the north of the city.
Smedile said the troops felt very welcome, with children following them everywhere. The troops were expected to spend five days helping to secure the hospital and capital city before being given their next assignment.
The medical needs are great after the 7.0-magnitude earthquake. Estimates say up to 200,000 people may have been killed. A Doctors Without Borders official has estimated the number of injured at 500,000.