The UN envoy to Yemen, Jamal Benomar, said on Friday that southern separatists and northern Shiite rebels have been invited to participate in a national dialogue set for November.
"Contacts have been made with all the parties, including the Southern Movement and the Huthis (Zaidis), to join the national dialogue and there is now agreement to begin the preparatory phase," Benomar said at the end of a two-week visit.
A dialogue aimed at facilitating political transition in Yemen was envisioned in the agreement that led to long-time president Ali Abdullah Saleh stepping down in February after months of deadly street protests.
The Southern Movement groups activists pushing for greater autonomy for the south and those who want full independence for the region, which was a separate state until 1990.
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Asked about its participation, Benomar said several factions had accepted the invitation, while presenting specific demands which he did not reveal.
However, he said the faction led by former vice president Ali Salem al-Baid, a southern leader, has refused to participate, but that contacts are still underway.
Yemen's mountainous north is a stronghold of the Zaidi Shiites, who from 2004 fought six wars with central government forces before signing a truce in February 2010. The rebellion claimed thousands of lives.
Benomar said the political process under Saleh's successor, President Abdrabuh Mansur Hadi, has "made a lot of progress" but that there "are still obstacles and challenges."
Key among them are a restructuring of the military, which was divided during the year-long popular uprising to unseat Saleh, and the campaign against Al-Qaeda, which is heavily active in the south.