The Oct. 27 talks in Addis Ababa, to be chaired by former South African President Thabo Mbeki, had hoped to address the status of Abyei, which is scheduled to decide next year whether to join north or south Sudan.

The vote on Abyei, which straddles the border between north and south Sudan, is due to be held on Jan. 9, 2011, the day southern Sudan votes on whether to secede from the north.

"Because we are still involved in the process of preparing for that, the meeting will certainly not take place on the 27th," Mbeki said late Monday after meeting President Omar Bashir. Mbeki hoped the talks happen soon.

Mbeki's comments made clear that despite a visit from US Senate Foreign Relations Committee chairman John Kerry last week, no agreement was reached on how to move forward with the Abyei vote.

One Sudanese official said north and south Sudan, which signed a peace deal in 2005 ending Africa's longest running civil war, could not reach a compromise on Abyei.

Failure to agree such a compromise will raise concerns of unrest ahead of the southern referendum, which most analysts expect to result in secession.

Abyei's administrator has rejected a US compromise to split Abyei in two with north and south each taking a section.

Ruling parties in north and south disagree on who will lead the commission to plan the Abyei vote and on who will be allowed to vote in the plebiscite.