The organisation also urged Sudan on Monday to accept a UN force in the troubled western region.
Alpha Oumar Konare, the AU commission chairman, said the pan-African body would ask the UN Security Council to impose sanctions on the Justice and Equality Movement (JEM) and a faction of the Sudan Liberation Movement (SLM) unless they signed the deal by Tuesday, when it is set to be implemented.
"I call on them to hasten to append their signatures, without any conditions, to the document, before its implementation on 16 May 2006," he told a meeting of the AU Peace and Security Council.
"Should they embark on any action or measure likely to undermine the (agreement), especially ceasefire provisions, the Peace and Security Council should take appropriate measures against them, including by requesting the UN Security Council to impose sanctions against them," Konare said.
The two groups have so far resisted pressure to sign the May 5 peace deal agreed in the Nigerian capital, Abuja, and signed by the Sudanese government and the main faction of the SLM.
SLA rejects pressure
Meanwhile, a rebel leader of the Sudan Liberation Army (SLA) has said he will not bow to intense international pressure to sign a peace agreement by the deadline because the government has rejected his conditions.
However, Abd al-Wahid Muhammad al-Nur wanted to keep trying to make a deal with Khartoum, and talks looked set to continue beyond the deadline because diplomats were desperate to gain wider support for the accord, a close adviser said.
Al-Nur (L) rejected the peace
accord signed on May 5
Nur rejected the peace settlement signed on May 5 by the Sudanese government and rival SLA factional leader Minni Arcua Minnawi to end a conflict that has killed tens of thousands.
The Abuja accord provides for a more equitable distribution of power and wealth, the disarming of the pro-government Janjawid militias and a referendum on the future of Darfur, but the holdouts say it does not go far enough.
Al-Nur's demands include greater compensation from Khartoum to Darfur war victims, more political posts for the SLA, and greater SLA involvement in the security of internal refugees returning home and in the disarmament of pro-government militias.
In his report to the Peace and Security Council, Konare, the AU chairman, also called on the Sudanese government to drop its objections to allowing UN peacekeepers to replace the current African Union mission in Sudan, known as AMIS.
"This is particularly pertinent given that the current mandate of AMIS will expire four-and-a-half months from now and the minimum lead-time the UN requires for an effective transition is six months," he said.
Lam Akol, Sudan's foreign minister, said Khartoum was ready to enter into talks with the world body about the scope and mandate of such a mission, but was not ready to welcome it.
"Sudan has rejected the transfer of the AU mission in Darfur to the United Nations," he told the meeting.
"At the same time, Sudan has reaffirmed its willingness to enter into dialogue with the UN.
"We still are sticking with this position and look forward to the time when these discussions with the UN will take place," Akol said.
Three years of war in the province between rebels and Khartoum, backed by their proxy militias, have claimed an estimated 300,000 lives and displaced about 2.4 million people.