The 15-member body unanimously adopted a resolution on Friday that also decided to extend for at least six months the mandate of the UN mission in south Sudan (UNMIS).
The text directed Kofi Annan, the UN chief, working with the AU and in consultations with the council "to expedite the necessary preparatory planning for transition" from the AU force known as AMIS to a UN operation.
This would include options for how UNMIS can provide transitional assistance - such as in logistics, mobility and communications.
Adam Ereli, US State Department deputy spokesman, said in Washington: "The unacceptable violence in western Darfur and on the Chad border has influenced the discussions in New York about the renewal of the UNMIS mandate in a way that we are looking to help facilitate the transition to a rehatted UN force by putting in language and procedures to strengthen that now and not have to wait for six months."Arab League's secretary-general as saying foreign troops should not be sent to Darfur without Sudan's consent.
In related news, Aljazeera on Friday quoted
"Darfur is a very important and sensitive case that should be dealt with in full co-ordination with the African Union," Amr Moussa said in Khartoum.
An AU peacekeeping force of
7000 troops is already in Darfur
Aljazeera quoted Mousa as saying he discussed with Omar al-Bashir, Sudan's president, developments in the region.
Moussa has said Darfur will be on the agenda at the Arab summit that opens in the Sudanese capital on Tuesday.
The Security Council resolution adopted on Friday also asks Annan to prepare recommendations within a month on how a separate UN peacekeeping mission in southern Sudan could help stop Uganda's Lord's Resistance Army, an armed group that has wreaked havoc in the region for decades.
The LRA has terrorised communities in Uganda's remote north for two decades, and some of its fighters have recently crossed over into neighbouring Democratic Republic of Congo and Sudan.
Led by self-proclaimed prophet Joseph Kony, the LRA has killed tens of thousands of unarmed villagers, slicing off survivors' lips or ears and abducting more than 10,000 children as fighters, porters and sex slaves.
The poorly equipped and under-financed AU force has proven ineffective in ending the violence, prompting Annan to call for its replacement by a bigger UN force.
Sudan's government, however, has said it does not want UN troops in Darfur until a peace agreement is reached in talks taking place in the Nigerian capital Abuja.
The AU's Peace and Security Council, bending under pressure from Sudan, voted this month to extend its mission in Darfur till September 30 while affirming in principle its plan to eventually hand over to a UN force.