The UN Security Council on Tuesday unanimously agreed to boost the number of UN troops and police in Haiti by 3,500 to help maintain peace and security and support earthquake relief efforts.
The full potential strength of the United Nations' Haiti force, known as MINUSTAH, will rise to 12,651, up from the current level of around 9,000.
Chinese UN Ambassador Zhang Yesui, council president for the month of January, told reporters after the vote that the reinforcements would have a six-month mandate but his words appeared to leave open the option that it could be extended.
All 15 members of the Security Council voted in favor of the resolution, which said the increase was a recognition of "the dire circumstances and urgent need for a response."
"I am ... grateful to the Security Council for their swift action," UN Secretary-General Ban Ki-moon told reporters, adding that it was "a clear signal that the world is with Haiti."
It was important to do everything necessary to get the additional forces on the ground as soon as possible, he said, adding that it could be done "quite quickly."
UN blue-helmeted troops have been struggling to help keep order and deliver aid after the Jan. 12 quake wrecked the Haitian capital Port-au-Prince and killed as many as 200,000 people.
UN peacekeeping chief Alain Le Roy told reporters the main task of the reinforcements would be to escort aid convoys.
US Deputy Ambassador Alejandro Wolff welcomed the increase in peacekeepers and made clear the United Nations, not the United States, was in charge of coordinating the humanitarian response to the disaster.
"The US effort there is to support the UN and the Haitian government," Wolff said. "We will support them how best we can."
More than 11,000 US military personnel are on the ground in Haiti but Wolff said he was not aware of plans for any of them to join the UN force.
Haiti's neighbor, the Dominican Republic, has offered an 800-strong battalion to form part of the MINUSTAH reinforcement.
Edmond Mulet, sent to Haiti to take over the UN mission after its chief, Hedi Annabi, and dozens of other UN staff died in the earthquake, said he understood Brazil was also offering more troops and France and Chile were offering police.
Speaking by videolink from Port-au-Prince, Mulet said he hoped those extra troops that were needed would be in place within two weeks.
"What we need from them is to be self-sustainable. They have to come with everything they need, because the mission is not really able to support them at this point," he said.
Ban raised concerns over haphazard aid efforts saying there was a risk that "unsolicited and uncoordinated supplies and personnel entering the country will stretch limited logistical resources and interfere with the delivery of vital aid."
He appealed to private aid groups to work closely with the United Nations "to make sure that our joint efforts complement one another."