CHRONOLOGY-Western Sahara -- a 50-year-old dispute

June 18 (Reuters) - Morocco and the Polisario Front are due to begin U.N.-sponsored talks on Monday to try to negotiate an end to Africa's oldest territorial dispute by settling the status of the former Spanish colony, annexed by Morocco after Madrid pulled out in 1975.

Here is a chronology of the Western Sahara dispute.

1884 - Spain colonises Western Sahara.

1957 - Morocco raises centuries-old historical claim to Western Sahara at the United Nations.

1973 - Polisario is formed and establishes itself as the sole representative of the Sahrawi people.

June 1975 - Morocco's King Hassan takes the territorial dispute to the World Court in The Hague. The court finds that some tribes had paid allegiance to Moroccan rulers, but rules that people should be allowed to settle the sovereignty issue through self-determination. Spain agrees to organise a referendum.

-- Nov. - King Hassan launches the Green March with 350,000 unarmed Moroccans crossing into the territory. Spain agrees to transfer administration of the territory to Morocco and Mauritania.

-- Dec. - Morocco sends in forces to occupy the territory.

1976 - As Spanish troops withdraw, Polisario guerrillas backed by Algeria and Libya proclaim the Saharan Arab Democratic Republic (SADR) with a government-in-exile based in Algeria.

1979 - Mauritania signs a peace deal with Polisario and renounces its claim to Western Sahara.

1980 - Morocco annexes Mauritania's share of the territory.

1984 - SADR is admitted as a member state to the Organisation of African Unity (OAU). Morocco leaves the OAU in protest.

1991 - U.N. brokers ceasefire, ending a guerrilla war between Polisario and Moroccan forces. The U.N. Mission for the Referendum in Western Sahara is established to oversee the ceasefire. A referendum is set for January 1992 which is postponed because of dispute over who is eligible to vote.

2001 - Former U.S. Secretary of State James Baker proposes autonomy for Saharawis under Moroccan sovereignty, a referendum after a four-year transition period, voting rights for Moroccan settlers resident in Western Sahara for over a year. Proposal rejected by Polisario and Algeria.

2003 - U.N. proposes Western Sahara becomes a semi-autonomous region of Morocco for a transition period of up to five years, to be followed by a referendum on whether the territory should become independent, semi-autonomous or integrated with Morocco. Polisario endorses the plan but Morocco rejects it, saying it will never give up sovereignty.

Aug. 2005 - Polisario releases 404 Moroccan prisoners of war - the last of 2,400 soldiers it had captured during the guerrilla war.

Oct. 2006 - Morocco calls a U.N. report critical of its human rights record in Western Sahara as biased in favour of the Polisario Front.

Dec. 2006 - The Moroccan advisory council proposes autonomy, burying the prospect of independence.

-- Polisario has already dismissed autonomy and the council's draft proposal. April 10, 2007 - Polisario says it proposes a "flexible" peace plan at the United Nations.

April 11 - Morocco unveils its plan to the United Nations.

June 18 - U.N sponsored talks begin.