FACTBOX: Who is attending Darfur talks and who is not

(Reuters) - Delegations from Darfur rebel groups, Sudanese government negotiators and international mediators gathered in Sirte, Libya on Saturday for peace talks aimed at ending 4-1/2 years of war in western Sudan.

The decision on the eve of the talks by two main Darfur rebel groups not to attend, however, cast doubt on the viability of the discussions.

Analysts say if the Libya talks lack support from key players any agreement coming out of them would likely suffer the same fate as a 2006 deal signed by only one Darfur faction. It did little, if anything, to end the violence.

Here are some details about the Darfur peace process and who may attend Saturday's talks:

* BACKGROUND:

-- Since the badly flawed 2006 Darfur Peace Agreement, signed by only one of three rebel negotiating groups, insurgents have split into more than a dozen factions, creating a chaotic security environment on the ground.

-- The first talks in Nigeria's capital Abuja were hindered not only by rebel divisions but by a disconnect between field commanders and the political leadership at the negotiating table.

-- The African Union-United Nations mediated talks in Sirte, Libya, to begin on Saturday, hoped to bring all those who have rejected last year's deal into the peace process.

* REBELS WHO WILL ATTEND PEACE TALKS: