Haiti's new prime minister has called for national reconciliation and an end to the dictatorships of the past after arriving back from exile.
Latortue hopes to lead Haiti out of political and social turmoil
Gerard Latortue, a former foreign minister and UN official, was appointed to form a transition government
and organise fresh elections.
In the aftermath of the successful rebellion against President Aristide, he said disarmament was essential.
The UN has warned Haitian children are at grave risk of hunger and disease.
And the security situation remains unsettled with US marines saying they had shot dead two armed men in the capital Port-au-Prince after coming under fire on Wednesday.
"The security problem is out of hand. Disarmament is imperative," said Mr Latortue, describing himself as a man of "compromise and unification".
He said he hoped the foreign peacekeepers would help retrain local police to "depoliticise them and make them more professional".
The new PM said he would consider re-establishing the army, dissolved by the ousted president in 1995 after human rights abuses.
Mr Latortue has lived in the US since 1988 but was nominated to be prime minister by a group of eminent Haitians earlier this week.
Meanwhile, Unicef, the UN's children's agency, said thousands were in need of medical attention.
The deputy director of its emergency programme, Eric Laroche, said many children had died of pneumonia or diarrhoea following the armed uprising against President Aristide, who left the country at the end of February.
Mr Aristide, now in the Central African Republic, is threatening legal action against the US and France, accusing them of abducting him and forcing him into exile.
The US has deployed just over 1,600 troops to Haiti
Armed Aristide supporters say they will revolt against any attempt to erase the legacy of the man they still consider their leader.
But US marines said they were launching a joint operation with Haitian police to take weapons from armed groups.
Marines Col Charles Gurganus told reporters in the capital, Port-au-Prince, that his men and the Haitian national police would "disarm men who are illegally armed" in public.
He called on Haitians to hand in weapons and pass on the names of those holding illegal arms.
The BBC's Daniel Lak in Port-au-Prince says the operation could bring the marines into conflict with Haiti's militias, especially supporters of ex-President Aristide.