ABUJA, Nigeria -- Two of the three rebel groups battling in Sudan's troubled Darfur region refused early today to sign a peace plan, jeopardizing the accord aimed at resolving a crisis that has cost at least 180,000 lives.
Abdelwahid Muhamed El Nur of the main rebel Sudan Liberation Army walked out of the meeting with negotiators, saying: ''We are not going to sign."
The action occurred shortly after the leader of a smaller group issued a similar declaration, while a splinter rebel faction said it needed time to consult with colleagues in Sudan and would return later in the morning.
The decisions followed days of intense talks that involved the African Union, rebels, and envoys from the United States, the European Union, and Britain. Deadlines for an accord were extended twice, and last night's session went several hours beyond the midnight time limit.
''These are all opportunities, but it requires leadership on the part of the movement that frankly is in question," US Deputy Secretary of State Robert Zoellick told reporters.
He said the meeting would resume at 9 a.m. local time with at least one of the rebel movements. He didn't name the group, but it will probably be the splinter faction.
Denis Sassou-Nguesso, president of the Republic of Congo and current head of the 53-nation African Union, said ''it has not yet ended."
Earlier, as the talks approached the midnight deadline, the Sudanese rebels had cautiously welcomed US-backed proposals to salvage the peace agreement for Darfur at the urging of the international community. Four pages of last-ditch revisions to the 85-page peace plan drawn up by African Union mediators offered concessions to the rebels on integrating fighters into the Sudan armed forces, compensation for war victims, and power-sharing. They were presented to the warring parties yesterday afternoon.
But as the session went well beyond the deadline, it became clear the rebels were unhappy with the plan.
El Nur didn't elaborate on the Sudan Liberation Army's position as he walked out. The other rebel faction rejecting the plan, the smaller Justice and Equality Movement, said the main sticking point was its demand for the post of second vice president.
''We decided not to sign it unless changes are made," said Justice chief negotiator Ahmed Tugod.
Decades of low-level tribal clashes over land and water in Darfur, a vast region about the size of France, erupted into large-scale violence in early 2003 with rebels demanding regional autonomy. The central government is accused of responding by unleashing Janjaweed militias upon civilians, a charge Sudan denies.
At least 180,000 people have been killed and more than 2 million forced to flee their homes in what the United Nations has called the world's worst humanitarian crisis. The conflict also has spilled into Chad and the Central African Republic.
The Sudanese government agreed to the initial proposal and has shown increasing flexibility since the United States and Britain sent top envoys to join the talks in Nigeria's capital. A spokesman indicated Wednesday that it could accept the US-drafted changes as well.
''We hope that the Americans' suggestion will be agreed upon," Sudanese government spokesman Abdulrahman Zuma said in an interview.
The European Union called on the rebels to come to a ''definitive agreement," and said failure would be ''irresponsible considering the enormous human suffering."
Foreign Affairs Minister Ian Pearson of Britain warned, ''The international community will not understand if they [the rebels] fail to take this opportunity to bring peace to Darfur and security to its people."
Revisions to the peace plan made available to the Associated Press called for 4,000 rebels to be integrated into Sudan's armed forces and 1,000 into the police force. In addition, 3,000 rebels would be given training and education at military colleges. The initial proposal mentioned no figures.
The new deal also would provide for rebels to constitute 33 percent of all newly integrated battalions nationwide and 50 percent in areas to be agreed upon, notably Darfur.
Zuma said Wednesday that his government had considered whether to integrate no more than 100 rebels into the armed forces and that he expected a final agreement to rest somewhere between that figure and the proposed 4,000. ''Through this so-called American initiative, it seems that the government is going to make some concessions, especially about reintegration and disarmament," he said.