The resolution, passed unanimously on Tuesday in the Ethiopian capital, Addis Ababa, requires Khartoum to allow UN military planners into Darfur within one week. 

Sudan has so far refused to allow UN personnel to visit Darfur to prepare for September's planned transition.

It has resisted a UN takeover of the 7,300 strong peacekeeping force and has given mixed signals since the May 5 peace deal it signed with Darfur rebels.

The UN also offered to strengthen the poorly-equipped AU force until it takes over.

John Bolton, the US ambassador to the UN, warned the Sudanese government that it "would find itself in a very difficult position if it didn't co-operate with this transition".

"I think if Sudan is doing anything other than reading the language of the resolution, which it should, it should also look at a 15-0 vote," Bolton added.

No longer relevant

The resolution also warned two rebel groups who have not signed up to the peace accord to do so and threatened "strong and effective" measures against anyone violating the agreement.

On Monday, Lam Akol, the Sudanese foreign minister, said direct UN-Sudan talks would be necessary before any UN force could be deployed.

He also said the peace agreement "rendered the issue of the transfer of AU mission to the UN no longer relevant".

Three years of war in the province between rebels and government-backed militias, have claimed an estimated 300,000 lives and displaced about 2.4 million people.