Sponsored by the African Union and United Nations, the meeting in the Tanzanian town of Arusha will seek to define a common stance among the rebels for a fresh round of peace negotiations with the Sudanese government.

When the deadly conflict erupted in the impoverished western Sudanese region four and a half years ago, the uprising against the central authority in Khartoum was spearheaded by one group.

Now diplomats face the daunting task of finding common ground for a dozen rebel factions, with one of the most significant ones missing from the talks.

"Our objective is to find a common position. You cannot have negotiations with on the one hand the Khartoum government and seven, eight or nine rebel groups on the other," African Union envoy to Sudan Salim Ahmed Salim told reporters Friday in Arusha.

The start of the talks was delayed until 1400 GMT as rebel delegations were only beginning to trickle to the venue of the talks.

The Sudan Liberation Movement (SLM) of Abdelwahid Mohammed Nur -- the rebellion's founding father and a member of Darfur's largest tribe -- is boycotting the talks, arguing that most factions have little legitimacy and that an effective ceasefire should be a precondition for dialogue.

"The more you recognise individuals as faction leaders by inviting them to talks like those in Arusha, the more factions there will be, and consequently disorder on the ground," Yahia Bolad, a spokesman for Nur, told AFP.

A Darfur peace deal was reached with the Sudanese government in May 2006 but it was only endorsed by one of three negotiating rebel groups. Violence has since spiralled and splinter factions have flourished.

The signatory was Minni Minawi, a military commander who broke away from Nur's group and is now the fourth-ranking official in the Sudanese state.

According to a recent report on Darfur rebels, the need is not so much for an effort to revive the Abuja peace deal but for a new and inclusive process.

"Abuja is dead. Moving forward requires starting from scratch. The most immediate hurdle remains the rebels' lack of unity and political vision," said the report, published last month by the Small Arms Survey.

Some factions have made an effort to streamline their unwieldy ranks ahead of the Arusha talks.

In mid-July, the leaders of five rebel factions gathered in the Eritrean capital agreed to form an alliance, the United Front for Liberation and Development, and invited other splinter groups to join.