WASHINGTON -- The 6,700-member African Union force sent to help prevent genocidal attacks in the Darfur region of Sudan has been unable to protect its own soldiers, let alone the 2 million displaced people living in camps there, humanitarian groups and regional specialists say.

The force, dispatched last year to monitor an unraveling cease-fire in an area roughly the size of France, has been targeted by government-backed militias, which attracted worldwide condemnation for attacking civilians, and by rebel groups that are fighting the government.

Two groups asserted this week in separate reports that the African soldiers do not have enough equipment or soldiers to protect themselves and they lack a mandate to take the offensive -- even when they have advance warning of planned attacks against civilians. The reports quoted members of the force. In the past two months, at least five African Union soldiers have been killed and 38 kidnapped.

''Things have been getting much, much worse now that attackers have seen there is no real consequence for targeting the African Union troops, internally displaced people, or the aid community," said Sally Chin of Refugees International, a Washington-based humanitarian group that issued a report calling for the African Union to increase its force in the short run, and eventually hand over the mission to the United Nations.

The Brookings Institution, a think tank in Washington, released a similar report this week. It called for 20,000 African Union troops on the ground, or for the United Nations, the European Union, or NATO to take over.

Hundreds of thousands of people have died from illness, starvation, and attacks in Darfur since 2003, when the militias, known as the janjaweed, began exterminating villages in an effort to wipe out a rebellion against the government. The conflict in Darfur erupted just as a separate, 21-year-old war was ending between Sudan's Arab government in the north and the black African rebels of the south.

The US government, immersed in negotiating an end to the north-south conflict, encouraged the African Union to take responsibility for Darfur, which US government officials -- including President Bush -- have termed a genocide.

But now US officials acknowledge that things are not going well.

''The fragile cease-fire in Darfur has been fraying," Deputy Secretary of State Robert Zoellick told an audience this week in Khartoum, Sudan's capital. Yesterday, Zoellick wrapped up his fourth visit of the year to Sudan after spending the week trying to persuade the Darfur rebel factions to adopt a common position in the peace talks and stop launching attacks on civilians and African Union soldiers.

A meeting with rebels on Tuesday in Kenya did not go smoothly. Initially, the two rival factions refused to meet one another, and a key rebel leader, Minni Arko Minnawi, never arrived.

During his trip, Zoellick emphasized in his remarks to reporters that the African Union's mandate in Darfur is to monitor the cease-fire, not enforce it, which would allow a far more aggressive military stance. The force is allowed to protect humanitarian operations and observers but may only protect civilians who are being attacked in the force's immediate vicinity.

Some human rights groups and Sudan specialists say the force's limited mandate makes the soldiers helpless witnesses to slaughter, much as the UN peacekeeping force was during the 1994 genocide of an estimated 800,000 Rwandans.

''This is hopelessly inadequate," said Eric Reeves, a Smith College professor who monitors events in Darfur. ''To pretend otherwise is to indulge a fiction that risks hundreds of thousands of lives. I think you see an increasing concern about the unfolding of a Rwanda-like event."

The African Union agreement with Sudan states that Khartoum has the primary responsibility for protecting civilians, even though the Sudanese government has been linked to numerous recent attacks against civilians.

Expanding the mandate of the African Union force would require the agreement of Khartoum, which is set to take over the rotating leadership of the union in January. So far, Sudan has denied the force the permission to transport 105 armored personnel carriers to Darfur, arguing that they could fall into the hands of rebels.

Some donor governments have also dragged their feet on assistance. Last week, US senators cut $50 million in contributions to the union's force from the 2006 budget bill.

The force has also faced difficulty with logistics and communication.

Still, the force -- made up mostly of Nigerian and Rwandan soldiers -- initially seemed to bring calm to the region as it increased its numbers this year to 4,890 soldiers, 686 observers, and 1,176 civilian police. But the past two months have seen an upsurge of violence against the force's soldiers and hundreds of civilian deaths.