The United Nations took partial control of the African Union's peacekeeping mission in Darfur Monday in a move meant to stem violence that has killed 200,000 people and driven 2.5 million from their homes.

But the new mission lacks necessary equipment and is staffed far below its authorized level, with only 9,000 of a planned 26,000 peacekeepers. Many international observers fear it will prove as powerless as the AU force it replaced.

The roughly 7,000 troops who made up the African Union force have been augmented by 800 U.N.-affiliated personnel and 1,200 policemen — meaning the new force has little additional strength.

In a ceremony at the new mission's headquarters outside the North Darfur capital of El Fasher, the AU force's commander, Gen. Martin Agwai, took off his green African Union beret and donned one with the blue U.N. colors — becoming the commander of the new force, known as UNAMID. The troops on hand for the ceremony did the same.

The ceremony capped months of international pressure on Sudanese President Omar al-Bashir to admit the U.N. force.

Al-Bashir's government has thrown up obstacles to the full deployment and Western countries have not provided military helicopters seen as key to making the force effective.

As a result, many experts inside and outside the U.N. believe the mission will have little immediate effect on improving security in Darfur after 4 1/2 years of violence. Ethnic African rebels have been battling troops of the Arab-dominated Khartoum government and the Arab militias known as janjaweed, which are accused of committing widespread atrocities against ethnic African civilians.

African Union spokesman Noureddine Mezni said additional troops from Egypt, Ethiopia and other countries were expected to arrive by mid-January, but he could not say how many. Building UNAMID up to its full strength of 26,000 "will take some months," he said. U.N. officials say many of the African forces are not prepared for a peacekeeping operation, and there is no clear timetable for their deployment. Also, no nation has offered the 24 helicopters the U.N. needs in Darfur.

Mezni said the force urgently needed military helicopters, better ground transportation and other equipment to be effective.

"In an area like Darfur, the size of France, we cannot do the job properly without these things. We appeal to the international community and all those able to provide us with these things to do so as soon as possible," he said.

AU troops have already given up on patrolling refugee camps or conducting most basic peacekeeping missions, such as protecting women from being raped by janjaweed when they trek out to collect firewood. Since they came under direct attack by rebels in September, most AU peacekeepers now stick to their bases.

Darfurians have placed high hopes in the U.N., and if they see the force as ineffective it could spark more violence. It could also further hinder the faltering progress made at brokering a new peace deal between Khartoum and rebels.

Al-Bashir long resisted Western demands that he accept a U.N. force, vowing with fiery rhetoric that he would lead a "jihad" against any U.N. peacekeeper who sets foot in Darfur. But in June he accepted a compromise deal for the deployment of a "hybrid mission" of mainly African troops.

Since then, the Sudanese government has refused to allow night flights — except for medical evacuation — or large U.N. cargo planes. It has also barred fully operational battalions of peacekeepers from Thailand or Scandinavia from deploying in January as planned.

More importantly, the two sides are still negotiating over a Status of Forces Agreement needed for peacekeepers to operate. Khartoum's proposals would have allowed the Sudanese army to scramble U.N. radio communications when it is conducting operations and require the peacekeepers to give the government advance notification for all movements.