The African Union's special envoy for the disputed Western Sahara warned Tuesday that Morocco's expulsion of most of the U.N. peacekeeping mission's civilian staff sets "a very dangerous precedent" for the U.N.'s far-flung missions and poses dangers to north Africa and the Sahel where extremist groups are operating.

Former Mozambican President Joaquim Chissano, whose appointment in 2014 was rejected by Morocco, told an informal meeting of the U.N. Security Council that the U.N. mission must be fully restored and the people of Western Sahara must be given "the opportunity of choosing freely their destiny," which is the only solution.

"The Western Sahara problem may be seen as a small problem," Chisano said, "but let us not forget that a spark may put a forest into fire and we should avoid that to happen."

Morocco annexed Western Sahara, a former Spanish colony, in 1975 and fought a local independence movement called the Polisario Front. The U.N. brokered a ceasefire in 1991 and established a peacekeeping mission known as MINURSO to monitor it and help organize a referendum on the territory's future that has never taken place.

Morocco considers the mineral-rich region its "southern provinces" and has proposed wide-ranging autonomy, but the Polisario Front insists on self-determination through a referendum for the local population — as called for in U.N. resolutions.

Last month, Morocco expelled most U.N. civilians after U.N. Secretary-General Ban Ki-moon used the word "occupation" in talking about Western Sahara following a visit to a camp for refugees from the region who have been in Algeria for over 40 years.

The U.N. says their departure has made it impossible for MINURSO to carry out its mandate. Ban, Chissano and many others have warned that the expulsion must be reversed because otherwise it will become a precedent and other countries with Security Council-mandated peacekeeping and political missions could decide to expel U.N. troops and staff as well.

Polisario Front Secretary-General Mohammad Abdulaziz also warned recently that unless Morocco is pressured to restore the U.N. mission, it will have a green light for military aggression. If that happens, he said, the people in Western Sahara will respond with "all legitimate means, including armed struggle."

Tuesday's informal Security Council meeting took place days before the April 30 expiration of MINURSO's mandate, at a time when members are struggling to agree on details of a U.N. resolution to extend the mission. The session was held in a U.N. conference room, not in the council chamber because France, a close ally of Morocco, has opposed any official briefing by the African Union envoy.

Chissano stressed that Morocco is part of Africa — even if it isn't an AU member — and "Africa bears a moral and political responsibility to find a solution to problems in the continent" and should play a leading role in resolving the Western Sahara dispute.

"We would very much like to continue dialogue, even with Morocco, but Morocco may not want to dialogue with the brothers in Africa, which we think is wrong," Chissano said.

He said renewing MINURSO's mandate "is a must" and a new resolution should also set a date for holding a referendum on Western Sahara's future and include human rights monitoring, which France has blocked.

Christopher Klein, the U.S. Mission's political coordinator, said the Obama administration supports "de-escalation" of the dispute between Morocco and the U.N., "a return to full functionality of the MINURSO mission," and the continuing "integrity of peacekeeping worldwide." He did not elaborate on what "full functionality" means.

France also supports "the full functioning of MINURSO," a council diplomat said, speaking on condition of anonymity because consultations have been private.