Mortars have again been fired near the centre of the Liberian capital, Monrovia, after a lull in fighting between government forces and rebels.
Up to 100 people are believed to have been killed by the explosions.
One mortar hit a building in the US embassy compound in the city shortly after some 40 American soldiers arrived to guard it.
The rebels have been fighting the regime of President Charles Taylor for more than three years.
US President George W Bush has said he might authorise the deployment of a small US peacekeeping force if President Taylor leaves the country.
Liberia was originally settled by freed American slaves in the nineteenth century.
