Senior officials from the main Democratic Republic of Congo (DRC) rebel group were prevented on Sunday from reaching the capital Kinshasa, to be sworn in the following day as members of an interim government.
The Rwanda-backed Congolese Rally for Democracy (RCD) said UN authorities in the eastern city of Goma had failed to supply enough planes to transport the 12 officials and their 150-strong retinue.
"The seven ministers, four vice-ministers and the secretary general of the transition government, all leaders of the RCD, have been waiting at Goma airport since 10am for the UN Mission in Congo (MONUC) to supply them with the means of reaching Kinshasa," a spokesman said.
"They must imperatively attend tomorrow's ceremony for the handing over of power from the outgoing government to the new transition government," said spokesman Crispin Kabasele-Tshimanga.
MONUC provided a 17-seat aircraft, but each of the 12 rebel delegates planned to travel accompanied by 15 bodyguards, as stipulated by a mutual agreement on security during the transition period, he said.
"Any action that aims to make the RCD ministers leave without their personal guard will be considered a blatant violation of the accords," said another rebel spokesman, Jean-Pierre Lola-Kisanga.
Kisanga blamed the outgoing government for putting pressure on MONUC not to supply the necessary fleet.
The head of the RCD on Saturday officially announced the end of his movement's five-year war against the Kinshasa-based government.
Addressing a gathering of some 15,000 people in Goma, RCD leader Azarias Ruberwa said the rebel movement's days as a "politico-military movement" were over and that it was now "a political party like the others."
With backing from Rwanda and Uganda, the RCD had taken up arms against then president Laurent Kabila in August 1998.
In June, the RCD and another rebel movement, the Congo Liberation Movement, signed up to a national transitional government led by president Joseph Kabila, who inherited the post on his father's assassination in January 2001.
The government is tasked with taking DRC through to its first democratic elections since those held after independence from Belgium in 1960.
Around three million people, mostly civilians, are estimated to have died during DRC's war, either as a direct consequence of hostilities, or because of related sickness and malnutrition.
While the RCD itself may have given up the fight against Kinshasa, a group closely allied to it, the Union of Congolese Patriots (UPC), based in Bunia, capital of the northeastern Ituri region, remains opposed to the government.
Tension was rising Sunday in Bunia after French peacekeepers shot dead four alleged rebel supporters, amid conflicting reports as to whether the four were armed or not.