AU commission chairman Alpha Oumar Konare, flanked by British Prime Minister Tony Blair, told a press conference in London that the accord sealed in Abuja, Nigeria, "will be credible if we can ensure the commitment becomes a reality."
"So we must lose no more time because if there is any doubt everything then can be questioned," he said after being asked when United Nations troops should be deployed to assist the 7,000-strong AU mission already on the ground.
"And we mustn’t forget the humanitarian aspects. In two months it will be the rainy season. If confidence doesn't reign again then... the situation could really worsen," the French-speaking official added through an interpreter.
Mr Konare hoped a UN mission could be deployed "as soon as possible" but acknowledged that securing agreement from UN members could take time.
Before backing Mr Konare, Mr Blair, whose government has now pledged more than 52 million pounds (A$130 million) to the AU mission, said resolving the situation was "an absolute priority" for his government.
Failure to implement the accord would have "very severe" consequences for hundreds of thousands of people in the war-torn western region, he added.
Access for military planners
UN chief Kofi Annan has asked Sudanese President Omar al-Beshir to allow UN military planners into strife-torn Darfur ahead of an anticipated UN operation.
Mr Annan, who is currently on an Asian tour, spoke with Mr Beshir by phone and told him he "hoped to see the UN assessment mission dispatched as soon as possible", spokesman Stephane Dujarric told reporters.
The UN Security Council last week unanimously approved a binding resolution urging speedy implementation of the peace accord reached earlier this month.
The 15-member body also called for the deployment of a joint African
Union-United Nations technical assessment team "within one week of the adoption of this resolution" to lay the groundwork for a handover of the AU peacekeeping mission to the UN.
Two senior UN officials -- retired troubleshooter Lakhdar Brahimi and deputy undersecretary general for peacekeeping operations Hedi Annabi –- have arrived in Sudan to discuss the planned deployment of UN peacekeepers in Darfur.
Decision to be made soon
Mr Beshir said that after his talks with Mr Brahimi, scheduled for Wednesday, he would discuss the issue with his government and a decision on whether to let the military planners in would be made shortly.
Mr Beshir's regime has not yet officially accepted a UN deployment in Darfur but senior officials have signalled that Khartoum is willing to be flexible on the issue.
Two smaller rebel factions have declined to sign the Darfur peace.
The AU has given them until May 31 to do so.
Around 10,000 UN peacekeepers are already deployed in mainly-Christian southern Sudan in a bid to bolster the January 2005 peace deal that ended 21 years of north-south civil war.
In his latest report on Darfur, Mr Annan meanwhile said the immediate priority for the world community must be to strengthen the 7,000-strong African Union force in Darfur (AMIS) "so that it can move ahead with implementing the agreement and providing real security for civilians."
Three years of war between rebels and Khartoum backed by proxy Arab militias have claimed some 300,000 lives and displaced 2.4 million in Darfur.
"Concrete requirements for support for AMIS include increasing the number of troops, and providing enhanced logistics and greater financial support," Mr Annan's report said.