The swearing in of a new transitional government in the Democratic Republic of Congo, which was due to have taken place on Friday, has been postponed.
France has requested a UN peace force for DR Congo
It was delayed because of a continuing disagreement between the government and rebels over the composition of a national army, the government said.
The setback came as the United States said it supported a French proposal for a multi-national peacekeeping force to be sent to the north-eastern town of Bunia, which has been wracked by fighting between rival ethnic militias.
The United Nations says it is increasingly worried about the situation in Bunia, capital of the gold-rich Ituri province, where local radio stations have begun broadcasting hate messages that threaten civilians.
Leaders of the main rebel group RCD-Goma, members of the government and the opposition are to be brought together in a new power-sharing administration.
RCD-Goma has accused the government of trying to keep control of the main army posts and military regions for itself.
Atanase Matenda, a spokesman for the body charged with setting up the transitional government, said it could not be sworn in until the dispute over the army had been resolved.
"We are obliged to reach an agreement," he told the UN news agency Irin. "The absence of RCD-Goma representatives is a big obstacle to the process."
Mr Matenda said attempts were under way to resolve the differences.
The United States, meanwhile, says it fully supports the French plan for peacekeepers in Bunia, which has been presented to the United Nations.
The US said it may provide logistical and financial support but ruled out contributing soldiers to the multi-national force.
The UK has announced it will send troops if the resolution is passed, which may happen later on Friday.
Correspondents say the exact size of the British contribution will not be decided for another few days, although it is likely to be less than 300 soldiers.
France has said the force could be in DR Congo in just over a week.
More than 400 people have been killed in Bunia in recent fighting between
rival Hema and Lendu groups, which erupted following the withdrawal of Ugandan troops from the area in early May.