The first contingent of 1,000 West African peacekeepers are to be deployed in Liberia within two weeks.
A US mission in Monrovia is assessing security
The decision follows a meeting of West African leaders and United Nations Secretary General Kofi Annan in Mozambique ahead of a summit of African Union leaders.
Rebels have launched two major assaults on the capital in recent months, and thousands of civilians have been displaced by the fighting.
Washington has not yet announced whether it will deploy any United States troops to help with peacekeeping, despite pressure to do so.
An American team of military experts is in the country on the second day of their mission to assess humanitarian and security needs.
Hundreds of Liberians gathered in pounding rain on Wednesday to greet the team visiting an airfield near the capital, Monrovia to evaluate whether the airfield could be used to fly in relief supplies.
The crowd of mostly women and children chanted "we want peace" as the team arrived.
The Americans are also expected to visit the port and Monrovia's main hospital.
On Tuesday, Mr Annan ordered an immediate resumption of UN humanitarian work in Liberia and the return of UN aid workers.
Mr Annan also appointed a senior US diplomat, Jacques Klein, as his top envoy to Liberia.
Earlier this week, the West African regional group, Ecowas, agreed to provide 3,000 troops for a peacekeeping force in Liberia.
Ecowas Executive Secretary Mohamed Ibn Chambas told the BBC it was vital to ensure the security of Monrovia.
He said the United States was supportive of the peacekeeping initiative, and would be sending military planners to Ghana for discussions later this week.
Ecowas estimates the cost of deploying the force and keeping them in place for the first six months at $100m.
BBC West Africa correspondent Paul Welsh said the promise may be for deployment in the next 14 days but it may not go as smoothly to the timetable as the Ecowas would like.
In the past, peacekeeping missions put together by the organisation have been slow to get into place because of financial and logistical problems, he said.
US President George W Bush has said that the first step to ensure peace in Liberia needs to be for President Charles Taylor - an indicted war criminal - to leave the country.
Mr Taylor has accepted a Nigerian offer of asylum but has said peacekeepers should come first to assure an orderly exit.
The UN refugee agency says it is struggling to cope with the thousands of refugees and displaced civilians who have converged on Monrovia after recent fighting between government and rebels.
The UNHCR says 15,000 refugees from Sierra Leone are living in camps on the outskirts of Monrovia, but many fled into the city as rebels tried to capture the capital.
Meanwhile, the Liberian government delegation at peace talks in Ghana says it wants Liberian Vice President Moses Blah to lead the transitional government after President Taylor steps down.
However, the main Lurd rebel group rejected the proposal on the transfer of power and also dismissed the idea of elections.