And a diplomatic tussle over the issue loomed as the Chadian foreign minister said his country would withdraw from the AU if Sudan took over the presidency.
Ahmat Allam-Mi told the Reuters news agency: "If (Sudan) gets it, Chad will withdraw from the African Union until al-Bashir is replaced."
Last year, wrangling over whether Sudan would take the chair dominated an African Union summit.
A compromise was reached that al-Bashir would take over this year in the hope that the situation would have improved in Sudan's west.
But security has deteriorated despite an AU-mediated peace deal in May and diplomats have said another battle over the year-long chairmanship may ensue.
However, Lam Akol, the Sudanese foreign minister, told Al Jazeera: "The chairmanship is not within the jurisdiction of the executive council. It is within the jurisdiction of the summit, and the summit decided in Khartoum last year that in 2007 the chairmanship would be for Sudan.
"And no one has the right to discuss this issue."
Jar el-Neby, a commander from a rival SLA faction which co-operates with the 7,500 AU peacekeepers in Darfur, also said the AU would not be able to mediate talks with Sudan as its head.
|Darfur rebel groups have said they will|
attack the AU if Sudan takes over [EPA]
"Definitely, if the government of Sudan becomes president of the AU we will fight with the AU," he said.
"There is no solution to the conflict in Darfur if Sudan becomes head of the AU. We refuse this and there will be no talks."
Human rights groups too have attacked the Sudanese government, saying it has failed to make genuine efforts to end what it says are the government's abusive policies in Darfur.
Peter Takirambudde, Africa director at Human Rights Watch, said: "Awarding Sudan the chairmanship would not only reward the sponsors of crimes against humanity in Darfur, it would irreparably discredit the AU."
Analysts have also said that the AU's relationship with the UN may be damaged by a Sudanese presidency.
Mark Seddon, Al Jazeera's UN correspondent, said Ban Ki-Moon, the UN secretary-general, may urge the Republic of Congo to hold on to the presidency of the AU for a further six months in attempt to resolve the impasse.
More than 200,000 people have been killed and 2.5 million driven from their homes in four years of conflict in Darfur.
The US has described the killings as genocide.