Government and rebel leaders from Sudan have begun the latest round of talks on the Darfur conflict.
Many are in refugee camps after fleeing fighting
Representatives of the Sudanese government and the two main rebel groups are present in Abuja, Nigeria.
However, one faction of the main SLM group is boycotting the talks, raising fears over their prospects of success.
Talks to try to resolve the conflict, in which 200,000 people have been killed and at least two million displaced, have had limited success.
"The inter-Sudanese talks have been extremely difficult and at times seem to have been conducted with complete disregard to the imperative of the situation on the ground in Darfur," said Baba Gana Kingibe, a top African Union official, at the opening session of the talks on Thursday.
But he remained optimistic, saying: "This round may turn out to be a turning point for the long suffering people of Darfur."
Members of one SLM faction, led by Abdul Wahid Nur, arrived in Abuja for the talks, but another, headed by Minni Minawi, stayed away.
Members of the dissenting group said they wanted the SLM's differences settled before it participates in talks.
The BBC's Yusuf Sarki Mohamed in Abuja says there is also another splinter group which sprang up last year which has not been invited.
It says it will not recognise anything agreed at the talks, our reporter says.
The AU-mediated negotiations had originally been due to begin last month, but were delayed to allow the rebels time to agree their positions.
Proposals include disarmament and increased autonomy for the people of Darfur.
Aid agencies say large-scale bloodshed seems to have been curbed in the region in recent months, and supplies to refugees are improving.
But the United Nations mission in Sudan says there have been a number of attacks on humanitarian workers in the past four weeks.