Diplomats say SLA Minnawi and his Chad chums one of main stumbling blocks to Darfur Peace Agreement
Observers say failure to get a deal would be disastrous.
"Nobody will look good, the AU, the government or the (rebel) movements, but the real victims will be the people on the ground," said Sam Ibok, head of the AU mediation team.
"They will not be able to return to their homes to cultivate their lands. They will have to spend more time in camps. Security will deteriorate. Women will continue to be exposed to rape and children will continue to suffer," he said.
The top two AU officials -- Chairman Denis Sassou Nguesso, the president of Congo Republic, and commission head Alpha Oumar Konare -- are due to arrive in Abuja on Wednesday. Diplomats said this could indicate that the 2300 GMT deadline, already put back by 48 hours, will slip again.
Diplomats said one of the main stumbling blocks to a peace agreement was that Minni Arcua Minnawi, leader of the most powerful of the three rebel factions, was being undermined by some of his former allies because of a crisis in Chad.
Minnawi is a tribal ally of Chadian President Idriss Deby, who is battling an insurrection by fighters he accuses of fronting for Sudan. But Minnawi's friends in Chad accuse him of abandoning Deby and selling out to Khartoum, which makes it difficult for him to sign any deal.