United Nations: The UN Security Council authorized on Tuesday up to 26,000 troops and police for Darfur and approved the use of force to protect civilians in Sudan's arid western region.

Expected to cost more than $2 billion in the first year, the combined "hybrid" UN-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 past four years.

UN Secretary-General Ban Ki-moon, who conducted months of talks with Khartoum, described the resolution as "historic and unprecedented" and said the mission would "make a clear and positive difference."

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 for self-defense, to ensure the free movement of humanitarian workers and to protect civilians under attack, but acknowledges Sudan's sovereignty.

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

Sudan's UN ambassador, Abdalmahmood Abdalhaleem Mohamad, told reporters, "I am comfortable with the resolution." He said the use of Chapter 7 was limited and that negotiators "went to great lengths to satisfy our concerns."

Specifically, the resolution authorizes up to 19,555 military personnel and 6,432 civilian police, which if deployed would be the world's largest peacekeeping force.

US Ambassador Zalmay Khalilzad called on Sudan's president, Omar Hassan Al Bashir, to provide "maximum cooperation" in deploying the peacekeepers or face sanctions.

"If Sudan does not comply with this resolution, the United States will move for the swift adoption of unilateral and multilateral measures," Khalilzad told the council.

"Now Sudan faces a choice," he said. "Sudan can choose the path of cooperation or defiance."

Visiting British Prime Minister Gordon Brown made a similar sanctions threat in a speech earlier in the day.

The revised text, however, dropped a threat to impose further sanctions.

China's UN ambassador, Wang Guangya, who chaired the meeting, said the purpose of the resolution was to launch the hybrid force "rather than threaten sanctions."

The measure was negotiated by Britain and France and also sponsored by Italy, Belgium, Congo Republic, Slovakia and Peru.