The United States military hopes to have Haiti's main port open again in the next few days, to receive emergency relief supplies for earthquake survivors.
The Port-au-Prince dock was badly damaged by a magnitude 7.0 earthquake on 12 January.
US media reportmore than 2200 US Marines arrived off the coast of Haiti on Monday aboard the amphibious ship USS Bataan. They are equipped with heavy lifting and earth-moving equipment, a dozen helicopters and medical support facilities.
The airport in Port-au-Prince is heavily congested, resulting in delays in distribution of relief supplies.
The BBC reports several agencies have complained about not being able to get aid through the airport.
The head of the US operation at the airport, Colonel Buck Elton, said on Sunday there had been 600 take-offs and landings since the United States took control on Wednesday. Fifty flights had been diverted.
He said about 60% of the flights coming in were civilian and 40% military.
US troops also said they had set up their first foothold outside the airport to deliver aid carried in by helicopters.
Many roads are still blocked by corpses and debris, hampering the delivery of fuel and other supplies.
Talks on road corridor
The UN says the Haitian and Dominican Republic governments are planning an alternative 130km road corridor to deliver relief from the southern Dominican town of Barahona.
The UN says it expects to resolve problems with bringing in fuel from the Dominican Republic in the next day or two.
Acute fuel shortages in Haiti could have serious implications: without sufficient fuel, the aid operation will come to a halt.