At least four of the numerous rebel groups in Darfur have agreed to work together, says the US envoy to Sudan.
Scott Gration said the deal reached in the Ethiopian capital Addis Ababa provided a “very strong foundation for rebel unification”.
He had earlier said that the existence of 26 different rebel groups was a major obstacle to bringing peace to the region after six years of conflict.
The UN believes that some 300,000 people have been killed.
The groups which have agreed to the “roadmap” are mostly splinter-groups from the Sudan Liberation Army (SLA).
Although factions originally from the Justice and Equality Movement (Jem) have not signed up, Mr Gration described the deal as “tremendous progress”.
Earlier, Sudanese Strategic Planning Minister Tajussir Mahjoub welcomed Mr Gration’s efforts to unify the rebels.
He told the BBC that negotiating peace with more than 20 groups was very difficult.
More than two million people have been forced from their homes in Darfur.
Earlier this week, Mr Gration said he had brokered an agreement to ease tensions between the main political parties in north and south Sudan.