Abuja, Nigeria ? Rebels in Sudan’s Darfur region on Sunday rejected a peace proposal that would end a conflict that has killed tens of thousands of people, but mediators extended the talks for two days under pressure from the United States.

Salim Ahmed Salim, a lead mediator for the African Union, said the talks would continue until midnight on Tuesday, pushing back the deadline for talks that have gone on for two years but so far failed to halt the bloodshed.

Earlier, the rebels called for changes to the deal – after the Sudanese government indicated it would accept the proposal.

Salim said the bloc had bowed to requests from the United States and others to continue negotiations.

“The African Union has extended the deadline of the peace talks by 48 hours as requested by the United States and other international partners to allow extensive consultations to go ahead,” he said at the talks’ site in the Nigerian capital, Abuja.

Years of fighting between ethnic groups and Arab militias in western Sudan have left at least 180,000 people dead and about 2 million homeless. Darfur’s violence recently spilled into neighboring Chad and threatens to escalate: Osama bin Laden last week urged his followers to go to Sudan to fight a proposed U.N. presence.

Amid the negotiations, the plight of 3 million refugees in Darfur has worsened. The U.N. World Food Program said Friday that it was cutting rations in half, citing a lack of funds.

Sudan has indicated it might accept a U.N. force in Darfur to aid African Union troops if a peace treaty is signed, and the head of Sudan’s delegation, Magzoub El-Khalif, said Sunday the government was willing to accept a draft resolution circulated last week.

The Sudanese government had said it was ready to sign the agreement. But a spokesman for one of Sudan’s rebel factions said the proposal does not adequately address implementation nor their key demands for a vice president from Darfur and more autonomy. Hahmed Hussein, a spokesman for the Justice and Equality Movement, said he was speaking for both rebel factions.

Among other provisions, a draft of the agreement circulated last week called for a cease-fire. But both sides have agreed to a truce before, only to keep fighting, even in the last week. The draft also calls for an infusion of funds into a region the draft document described as “historically deprived.”

Hussein, the rebel spokesman, said the agreement was “imbalanced.”

“We are not going to sign it as it is,” he said.

The other main rebel group, the Sudan Liberation Movement, had asked for more time.

The initial draft released Wednesday addressed complaints from Darfur rebel groups that they had been neglected by the national government. It called for the president to include a Darfur expert, initially nominated by the rebels, among his top advisers.

In the draft, mediators also proposed that the people of Darfur vote by 2010 on whether to create a single geographical entity out of the three Darfur states, which would presumably have more political weight.

Decades of low-level tribal clashes over land and water in Darfur erupted into large-scale violence in early 2003 when some ethnic groups took up arms, accusing the east African nation’s Arab-dominated central government of neglect.

The central government is accused of responding by unleashing Arab tribal militias known as Janjaweed to murder and rape civilians and lay waste to villages. Sudan denies backing the Janjaweed.

The draft agreement calls for disarming the Janjaweed and integrating some rebels into the national army and security forces.