The inaugural meeting of the new power-sharing government in the Democratic Republic of the Congo has failed to take place.
Four vice-presidents were inaugurated on Thursday
The delay follows the refusal of ministers from two main rebel groups to take part in a swearing-in ceremony on Friday.
They accuse President Joseph Kabila of trying to extend his powers under the transitional government, which is supposed to end a war which has raged for almost five years, killing an estimated three million people.
The rebels say Mr Kabila is head of the republic, not the government in the transitional authority, and making an oath of allegiance to him is unconstitutional.
The BBC's Ishbel Matheson in the capital, Kinshasa, says it may seem like a trivial complaint but the jockeying for political power is under way.
The row comes just days after the inauguration of four new vice-presidents, including two rebels, raised hopes of an end to Africa's bloodiest war.
However, our correspondent says it will not scupper the transitional government, as it is in the interests of both sides to seek compromise and move the peace process forward.
No date has so far been announced for when the meeting will take place.
Earlier this week, an official with the rebel RCD, Crispin Kabasele-Tshimanga, said that the ministers "did not want to consecrate a new dictatorship" or "personality cult" by swearing loyalty to Mr Kabila.
Other ministers in the new government took their oath of office on Tuesday but the RCD ministers delayed their arrival in Kinshasa in a row over how many bodyguards they would be allowed to take to the capital.
On Thursday, Azarias Ruberwa, RCD leader and new vice-president, said: "Our arrival marks the effective start of the transition."
"We have already announced the end of the war, now it's a reality."
The new government is supposed to organise the first multi-party elections since DR Congo's independence in 1960.
Even before this latest set-back, analysts said that unifying a country four times the size of France, across which there are few linking roads or railways, will be a huge task which could take many generations.