At least 200 000 people are estimated to have died and 2,1-million chased from their homes since the conflict flared in 2003, when non-Arab rebels in the Darfur region of Sudan began fighting the Arab-dominated Khartoum government.

The mediators have been criticised for a lack of progress in bringing the rebel groups to talks and there is still no decision on when and where the negotiations will take place and which of the rebel factions will attend.

United Nations peace envoy Jan Eliasson was joined in Tripoli by the envoys of the United States, the European Union and China and foreign ministers of Chad and Sudan, Libyan news agency Jana reported.

They were expected to assess progress in meeting preconditions for the talks to begin and try to fix a new timeline.

Eliasson has said he now hoped the end of next month would at least see a decision on the names of the rebel groups who will attend the new talks.

The rebel's continued failure to find a united negotiating stance has slowed progress. They split into more than a dozen armed groups after an unpopular peace deal last year with Khartoum that only one group signed.

On Saturday, five of the groups agreed to unite to end the four-year conflict and called on other groups to join them.