Malian Islamist rebel group Ansar Dine can be part of a negotiated political solution to reunite the divided West African country if it breaks with al Qaeda and its allies, a senior African Union official said on Monday.African leaders at an AU summit in Addis Ababa are backing negotiations to try to form an inclusive national unity government in Mali, where a March 22 military coup in the southern capital Bamako triggered the seizure of the north of the nation by a mix of Tuareg separatists and Islamist rebels.Since then, the Islamists, some allied with al Qaeda, have displaced local Tuareg separatists to seize control of most of the largely desert north, including the main towns of Gao, Kidal and Timbuktu. They include Ansar Dine, a Malian group led by a prominent Tuareg fighter and political leader, Iyad Ag Ghali.Parallel to the negotiations, the AU through the West African regional grouping ECOWAS is pursuing a plan to create a military force which, with U.N. backing, would intervene to expel the northern rebels and reunify Mali if the talks failed."We have not yet exhausted all the possibilities to reach a peaceful solution to this situation,” AU Peace and Security Commissioner Ramtane Lamamra told reporters at the summit.While the AU has ruled out negotiations with what it calls "terrorist groups” such as al Qaeda and its allies like Boko Haram in Nigeria and al Shabaab in Somalia, regional mediators were maintaining contacts with the Malian Tuareg-led MNLA movement and Ansar Dine, Lamamra said.He welcomed the fact that the MNLA (National Movement for the Liberation of Azawad), which originally led the successful rebellion in the north, declared on Sunday it had dropped its claims for a separate state after the northern revolt was hijacked by the al Qaeda-linked Islamists.Lamamra said Ansar Dine could still also join the dialogue to form a national unity government for Mali, which he said should include influential figures from the north.