Expected to cost more than $2 billion in the first year, the combined United Nations-African Union operation aims to quell violence in Darfur, where more than 2.1 million people have been driven into camps and an estimated 200,000 have died over the last four years.

UN Secretary-General Ban Ki-moon described the resolution as "historic" and urged member states to offer "capable" troops quickly.

The resolution, number 1769, invokes Chapter 7 of the UN Charter, under which the United Nations can authorize force. The measure allows the use of force to be used for self defense, to ensure the free movement of humanitarian workers and to protect civilians under attack.

But the resolution, which has been watered down several times, no longer allows the new force to seize and dispose of illegal arms. Now they can only monitor such weapons.

Gone also is a threat of future sanctions, but British Prime Minister Gordon Brown warned on Tuesday that "if any party blocks progress and the killings continue, I and others will redouble our efforts to impose further sanctions."

"The plan for Darfur from now on is to achieve a cease-fire, including an end to aerial bombings of civilians; drive forward peace talks ... and, as peace is established, offer to begin to invest in recovery and reconstruction," he said on a visit to the United Nations.

Britain and France are the main sponsors of the resolution.

Specifically, the text authorizes up to 19,555 military personnel and 6,432 civilian police.

Troops Mostly from Africa

The resolution calls on member states to finalize their contributions to the new force, called UNAMID or the United Nations-African Union Mission in Darfur, within 30 days. UNAMID would incorporate the under-equipped and under-financed 7,000 African Union troops now in Darfur.

Rape, looting, murder and government bombardment drove millions from their homes in Darfur, where mostly non-Arab rebels took up arms in early 2003, accusing Khartoum of neglecting their arid region. The rebels have now split into a dozen groups, many fighting each other.

Sudan, after months of hesitation, has agreed to the troop numbers, but UN officials expect it will take a year to get the force in place. Khartoum also has to agree to allow units from individual countries into Sudan.

Infantry soldiers will be drawn mainly from African nations unless not enough Africans can be recruited. Personnel from elsewhere in the world are expected to be used for specialized engineering and in command headquarters. The United States is restricting its contribution to transporting troops to Darfur and helping to pay for the operation.

The new headquarters should be running by October 31, and UN members were urged to cover costs as soon as possible for the under-financed African Union troops.

The timetable is then staggered so the combined force will be in charge of all operations by December 31.

The resolution asks Secretary-General Ban Ki-moon to report to the council every 30 days on implementation of the resolution and progress on a political settlement. The United Nations and the AU are attempting to organize a peace conference among a myriad of rebel groups and the government.