The Sudanese government and two rebel groups in the country's restive Darfur region have agreed to resume peace talks next month in Abuja, Nigeria, according to African Union officials.

Peace talks between the Khartoum government and Darfur's two main rebel factions were scheduled for this week, but were postponed after the Sudan Liberation Movement, the region's largest rebel group, said it was not ready. SLM wanted to delay the talks until October.

But after three days of informal meetings in Tanzania, led by the African Union's chief mediator, Salim Ahmed Salim, the Sudanese government and rebels agreed to meet September 15.

It will be the sixth round of talks aimed at ending the conflict in Sudan's Darfur region, which has triggered what the United Nations consider the world's biggest humanitarian crisis.

"Sudan's government has announced that it is going for negotiations in September. We wanted it to be before that, but still we are waiting for the rebel groups to announce their position," said Abu Zeid,  Sudan's foreign affairs minister and his country's representative to the African Union. "They have had some differences in their ranks and that's why they stopped negotiations. So they asked the U.N. [AU] mediator for some time so they can patch their differences and come back."

Sudan's government and Darfur rebels agreed on a declaration of principles in earlier peace talks that called for a return of refugees and beefed up security in the region.

Mr. Salim, the AU negotiator, says the new talks are expected to focus on issues related to the sharing of political power and natural resources.