"A package has been put together and presented to the parties, but there are no takers yet," said a senior member of a U.S.-led diplomatic team involved in talks between the two sides in the Nigerian capital Abuja.

"What we are saying to the (rebels) is, 'Please take it and then we can put pressure on the government'," said the diplomat, requesting anonymity.

He said it was possible the parties would agree to the new peace package at a meeting due to take place at the Nigerian presidential villa but there was no certainty.

The government accepted the African Union's original proposals on security, power-sharing and wealth-sharing but three rebel factions from Sudan's western Darfur region objected to many provisions.

African Union (AU) mediators have twice put back by 48 hours a deadline for an agreement to allow more diplomatic efforts, now being led by U.S. Deputy Secretary of State Robert Zoellick.

"The gaps between the parties are so wide that only the kind of concerted international pressure we're seeing here has a chance of working," said a Western diplomat closely involved in the talks, asking not to be identified.

Rebels took up arms in early 2003 in ethnically mixed Darfur, an arid region the size of France, over what they saw as neglect by the Arab-dominated central government.

Khartoum used militias, known as Janjaweed and drawn from Arab tribes, to crush the rebellion. Tens of thousands of people have died, while a campaign of arson, looting and rape has driven more than 2 million from their homes into refugee camps in Darfur and neighbouring Chad.

"The scenario of failure is very scary. You can be sure that the government would go after (the rebels)," said another Western diplomat, adding that parties blocking a deal would probably face U.N. sanctions.

Zoellick's team, along with Britain's International Development Secretary Hilary Benn and a host of European Union and Canadian diplomats, shuttled between government and rebel delegations.

Nigerian President Olusegun Obasanjo and Congo Republic President Denis Sassou Nguesso, who is also AU chairman, were due to hold a series of separate meetings with the parties involved, the AU's chief mediator Salim Ahmed Salim said.

A senior AU source said the midnight deadline was likely to slip but only for discussions to continue late into the night.

"The clock will stop at midnight but this is it. There is no extension," he said.

The thrust of a U.S. proposal was that Khartoum should accept a detailed plan for rebels to be integrated into Sudan's armed forces, a key rebel demand.

In exchange, part of the draft deal that says Khartoum must disarm the Janjaweed before the rebels lay down their weapons would be amended to better suit the government.

The rebels are split into two movements and three factions with complex internal politics and a history of infighting, making it hard to agree on any major decision. So far, they have said they were dissatisfied with many aspects of the draft.

For example, they want a post of Sudanese vice-president, a new regional government, greater representation in both national and local institutions, and individual compensation for victims of war. Mediators say they have been inflexible on these points.

Peace talks have dragged on for two years in Abuja while violence has escalated in Darfur to the point that aid workers cannot reach thousands of refugees.

Further complicating the situation is a crisis in Chad, which the rebels use as a rear base and where President Idriss Deby is battling insurgents he accuses Sudan of supporting.

"The situation (in Darfur) is poor, bad and very alarming," Louise Arbour, U.N. high commissioner for human rights, told Reuters in Khartoum after a two-day visit to Darfur this week.

Aid workers say a deal is vital before the rainy season begins in June when planting of food crops must be completed.