Warring factions from Sudan's Darfur region are facing a midnight deadline (2300 UTC) to agree on a deal to end three years of civil war.
African Union mediators and top U.S. and British diplomats are pressing the Khartoum government and two rebel groups to sign a peace plan by Thursday night after postponing the deadline twice already.
Talks now headed by U.S. Deputy Secretary of State Robert Zoellick went late into the night on Wednesday in the Nigerian capital, Abuja.
Sudan's government is considering a modified peace proposal, including calls for it to disarm Arab militias in Darfur more quickly and to integrate more rebels into its security forces.
Zoellick and Britain's International Development Secretary, Hilary Benn, proposed changes to the original plan after rebel leaders rejected it.
The rebels have not said whether they will accept the new proposal.
A conflict over land and water resources in Darfur erupted into fighting in 2003 when non-Arab rebels accused the Arab-dominated government of neglect. Fighting between the rebels, government forces and Khartoum-backed Janjaweed militias has killed at least 180,000 people and displaced more than two million others.
The United States has accused Sudan of a campaign of genocide against people living in the western Darfur region.Some information for this report was provided by AFP and Reuters.