The deadline for peace talks to end bloodshed in Sudan's western Darfur region was extended by 48 hours on Sunday, after rebels rejected a proposed deal to halt the fighting that has left tens of thousands of people dead.

United Nations representative Jan Pronk, right, speaks with Dr. Magardo Ahmed, advisor to the president of Sudan, between meetings at the Darfur peace talks in Abuja, Nigeria Sunday, April 30, 2006. [AP]

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 violence.

Earlier, the rebels called for changes to the deal ¡ª 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.

In Washington, actors, athletes, politicians and religious leaders rallied to call attention to the Darfur conflict and urge greater U.S. involvement in ending what the United Nations has called one of the world's worst humanitarian disasters.

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 is willing to accept a draft resolution circulated last week.

Secretary of State Condoleezza Rice called on China and Russia to join the United States in pushing Sudan to accept U.N. forces.

At the rally in Washington, the crowd chanted "Not on our watch" as a parade of speakers lined up for their turn on a stage on the National Mall, the Capitol serving as a backdrop.

"The personal motivation for a lot of us is the Holocaust," said Boston-based Rabbi Or Rose of Jewish Seminarians for Justice. "Given our history and experience, we feel an obligation to stand up and speak out."

Among those headlining the Washington rally was the actor George Clooney.

"You feel completely overwhelmed," Clooney, just back from a trip to Africa with his father, told AP Radio News ahead of the rally. "We flew over areas and my father and I would look at each other and go, this is just too much. But then what are we to do? Nothing?"

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.

Sudan announced its readiness to sign earlier Sunday ¡ª after it became clear the rebels were not ready to reciprocate.

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.

An agreement between Sudan and the rebels likely would be seen as a triumph of African diplomacy. The talks have been organized by the 53-nation African Union, with key participation from leaders from South Africa and Nigeria.

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.