KHARTOUM, Sudan (AP) — A key Darfur rebel leader warned Saturday his movement will not attend peace talks with the government this month unless the United Nations and the African Union can persuade a rival group to unite its splinter factions for the negotiations.

The military power of Khalil Ibrahim’s Justice and Equality Movement makes its participation crucial to the success of the talks, set to begin Oct. 27 in Tripoli, Libya.

Ibrahim had previously said he would attend the talks, meant to end more than four years of fighting between ethnic African rebels in Darfur and the Arab-dominated Sudanese government. But on Saturday, Ibrahim said he would stay away unless the rival Sudan Liberation Army united its factions.

Ibrahim said U.N. and AU mediators were lagging behind schedule in organizing the talks and determining which groups should attend. He said his movement would not negotiate with multiple factions that have limited support.

“There must be only three sides in Tripoli: JEM, SLA, and the government,” Ibrahim told The Associated Press by satellite phone from Darfur. “If the mediation fails to decide this very precisely, JEM will not come to Tripoli.”

Instead, Ibrahim said his movement would negotiate its own agreement with the government without U.N. and African mediation.

U.N. mediators did not return calls for comment late Saturday, the end of the weekend in Sudan.

A Darfur peace agreement reached in May 2006 failed to bring peace in large part because only one rebel chief, Minni Minawi, accepted it.

Minawi heads the main SLA faction but has lost much of his following since he signed the deal and became a high-ranking government official.

JEM claims to have thousands of troops in Darfur, though independent observers believe the number of regular, trained fighters is far fewer. The nearly a dozen SLA splinter groups collectively have more fighters.

But JEM has led rebel coalitions that have repeatedly defeated the Sudanese army in combat. In recent weeks, the movement claimed to have downed several government planes and helicopter gunships, and killed dozens of troops, countering a government offensive in eastern Darfur.

Observers in the area have largely confirmed these claims.

A second key Darfur rebel chief, Abdul Wahid Elnur, has also refused to attend the Tripoli talks. Elnur founded the SLA but is believed to have lost much control over the armed factions. But his role remains crucial, because he is believed to have the largest civilian following in Darfur. His tribe, the Fur, is the largest in the region to which it gave its name.

Elnur says he will only negotiate once a planned force of 26,000 U.N. and AU peacekeepers arrives in Darfur to protect ethnic African civilians.

An African Union force of 7,000 peacekeepers now on the ground has been unable to end the violence that has displaced more than 2.5 million people and left more than 200,000 dead since February, 2003. Ten AU peacekeepers were killed in a suspected rebel attack on the base of Haskanita last week.