Morocco, Algeria, Mauritania and the Polisario Front have accepted a UN invitation to hold talks in December on ending the decades-old conflict in Western Sahara, according to UN officials.The United Nations has repeatedly failed to broker a settlement over the north African territory, where Morocco and the Algerian-backed Polisario fought for control from 1975 to 1991. Seeking to re-launch the political process, UN envoy Horst Koehler has invited the four parties to Geneva on December 5-6 for a first round of meetings that could pave the way to formal negotiations.Koehler, a former German president and ex-director of the International Monetary Fund, last month sent letters of invitation to the talks and set an October 20 deadline to respond.Morocco and the Algerian-backed Polisario Front told the United Nations they would attend earlier this month. Algeria and Mauritania also recently said they would take part, according to a UN official.The last round of UN-sponsored informal talks was held in 2012.The preliminary talks may quickly hit a wall as Morocco maintains that negotiations on a settlement should focus on its proposal for autonomy for Western Sahara.The Polisario insists that the status of the territory should be decided in a referendum on independence.Algeria also maintains that a solution to the conflict must uphold the right of the people of Western Sahara to self-determination.The United Nations brokered a ceasefire deal between Morocco and the Polisario in 1990 that provided for a referendum, but the vote never materialized.A small peacekeeping mission of some 700 personnel is monitoring the ceasefire line but the Security Council has put fresh pressure on the sides to return to the negotiating table.A settlement in Western Sahara would allow the UN mission there, known as MINURSO, to end its mission at a time when the United States is seeking to reduce the cost of peace operations.In his invitation to the parties, seen by AFP, Koehler asked the sides to submit proposals for talks and has described the Geneva meeting as a round-table discussion. The planned talks will be discussed at the Security Council later this month as it weighs a mandate renewal for MINURSO.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.