On Friday the council authorised UN officials to draw up a range of options for the operation.

The 15 council members said in a statement they looked forward to a decision by the African Union, which has 7000 monitors and soldiers in Darfur, to transfer its operation to the United Nations.

The council asked Kofi Annan, the UN secretary-general, to "initiate contingency planning without delay" and produce a range of options in consultation with the AU.

John Bolton, the US ambassador to the UN and current council president, said: "The purpose of today's statement was to kick off contingency planning.

"And my instructions, and my intentions are very clear, which (are) to move as far and as fast as we can during the month of February."

Decision process

The African Union, the only bulwark in Darfur to prevent killings, rape and pillaging, supports "in principle" joining or relinquishing its mission to the United Nations.

But the AU will not take a final decision until late March, which means the council cannot authorise a UN force before then. The Sudan government has also not agreed.

Annan has suggested aggressive, highly mobile units that few nations could provide. Bolton said no decision had been made about US involvement.

The Darfur conflict erupted into violence in early 2003 when African tribes took up arms accusing the Khartoum government of neglect. The government retaliated by arming militia, known as Janjawid, who began a campaign of murder, rape, arson and plunder and drove two million villagers into squalid camps. Khartoum denies responsibility.

The top UN envoy in Sudan said last month international efforts to bring peace to Darfur had failed.

Jan Pronk told the council: "All we did was picking up the pieces and muddling through, doing too little too late."

He estimated 20,000 troops would be needed to disarm marauding militias and protect refugees who want to go home, but UN officials say this number is too high.