The two sides ended their decades long ruinous civil war in 2005 with a peace deal that created a unity government and afforded the south a semiautonomous status. But that agreement, including a resolution to their competing claims of Abyei, was never fully implemented because of foot dragging on both sides.
At one point, the southerners left the country's unity government for several months before eventually returning.
Sunday's deal provides new hope, though, as it is the first time the rivals have agreed to international mediation in the dispute.
In a ceremony late Sunday, the two sides spelled out the details of the agreement, which also promised the U.N. free movement around the area, also a first.
"This problem of Abyei, which was to undermine the unity in Sudan, will thank God, be used for building a unified Sudan," al-Bashir told the crowd.
At the time of the 2005 peace deal, a border proposed by an international commission would have put Abyei in the south, but was rejected by the north, and the region was accorded a special status.
During the relative calm that followed the deal, oil fields between the north and south, many of which are in Abyei, were developed. But fighting has continued to flare in the area. Weeklong clashes last month drove up to 90,000 people from their homes, burned the town of Abyei to the ground, and left at least 22 soldiers dead and hundreds injured.
The new roadmap, drafted over the past week, will allow the tens of thousands of the displaced to return. It sets up an interim administration to be headed by a southerner from Abyei appointed in two weeks time. His deputy would be from al-Bashir's party, according to the agreement.
Sunday's deal includes a commitment to a final resolution of the Abyei question. The two sides will choose an international arbitration agency to draw the border, and they agreed to be bound by its decision.
