A United Nations delegation is holding talks in Nigeria on building a peacekeeping force for Liberia.
Thousands have fled the fighting
UN Secretary General Kofi Annan, along with the French Foreign Minister Dominique de Villepin, has called for a multinational force to take action to avoid a "major humanitarian tragedy".
But so far, there is no agreement on what shape the force should take.
A fragile ceasefire was shaken overnight as government militias fired shots and looted in the capital, Monrovia.
The BBC's Dan Isaacs in Lagos says Nigeria, the regional military giant, will play a crucial role in deciding what should be done.
Pressure on America
The UN Security Council mission is meeting Nigerian President Olusegun Obasanjo and members of the Ecowas regional grouping to discuss the possibility of sending a West African-led force.
But there is also pressure on the United States - which has strong historical ties to Liberia - to take a lead role in peacekeeping.
Britain and France - which have intervened in conflicts in their former colonies in West Africa - have urged Washington to take a stand.
And Liberian President Charles Taylor has asked for the US to promote peace, despite a call by US President George W Bush for Mr Taylor to step down.
Washington says it has no plans to commit troops.
Aid agencies in Monrovia have had some of their vehicles stolen in the overnight looting, hampering their efforts to help the estimated 250,000 people who are living rough after fleeing their homes.
Fuel supplies have also been taken by the government militias.
Up to 300 people are reported to have been killed and 1,000 injured during two days of mortar fire into the heart of the city last week.
The main rebel group, the Liberians United for Reconciliation and Democracy (Lurd), who are demanding the removal of President Taylor, declared a unilateral ceasefire on Friday to avoid a "grotesque humanitarian catastrophe".