On the table was a document drawn up by African Union (AU) mediators after two years of talks on ending the conflict in Sudan's arid western Darfur region, amended in the past two days by a US-led diplomatic team to try to win rebel acceptance.
The Sudanese government accepted the African Union's (AU) original proposals on security, power- and wealth-sharing, but three rebel factions from Darfur raised objections in all three areas.
AU mediators had twice put back by 48 hours a deadline for an agreement to allow more diplomatic efforts, now being led by Robert Zoellick, the US deputy secretary of state.
The final deadline was midnight (2300 GMT) on Thursday.
A Western diplomat closely involved in the talks, asking not to be identified, said: "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."
Another Western diplomat said that parties blocking a deal would probably face UN sanctions. "The scenario of failure is very scary," he said. "You can be sure that the government would go after [the rebels]."
"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"
Zoellick's team, along with Hilary Benn, Britain's international development secretary, and a host of European Union and Canadian diplomats shuttled between government and rebel delegations.
A senior AU source had predicted that the midnight deadline would slip but only for discussions to continue into the early hours.
Salim Ahmed Salim, the AU's chief mediator, said that Olusegun Obasanjo, the Nigerian president, and Denis Sassou Nguesso, the president of Congo Republic who is also AU chairman, were due to hold a series of separate meetings with the parties involved.
"The clock will stop at midnight but this is it. There is no extension," he said.
The thrust of a US 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 Janjawid militias before the rebels lay down their weapons, would be amended to better suit the government.
Mediators say that the rebels have been inflexible on wanting 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.
The conflict has forced our two
million people from their homes
Peace talks have dragged on for two years in Abuja while violence has increased in Darfur to the point that aid workers cannot reach thousands of refugees.
Rebels took up arms in early 2003 in ethnically mixed Darfur over what they saw as neglect by the Arab-dominated central government.
Khartoum used militias, known as Janjawid 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 two million from their homes into refugee camps in Darfur and neighbouring Chad.