Addis Ababa - African Union heads of state will decide on Monday whether to readmit Morocco after a 33-year absence. Looming over that decision is the decades-old dispute over the Western Sahara.The former Spanish colony is the last territory on mainland Africa whose post-colonial future has yet to be decided.Rabat walked out when the African bloc admitted the Saharawi Arab Democratic Republic declared by the pro-independence Polisario Front at the height of a 1975-1991 war over the territory.By the time the fighting ended with a UN-brokered ceasefire, Morocco controlled 90 percent of the territory, including its three main towns, and insists it is an integral part of the kingdom.But the SADR, which remains a member of the AU, insists the territory's future can only be decided in a UN-supervised referendum in accordance with a 1975 decision by the International Court of Justice.One was supposed to be held in 1992 but was aborted when Morocco objected to the proposed electoral register, which it said was biased in favour of independence.Peace initiatives The UN peacekeeping mission which attempted to organise the vote has remained in the territory ever since, monitoring the 2 700km long sand wall built by the Moroccan army across the desert that separates the two sides.Repeated peace initiatives have gone nowhere with Morocco insisting there can be no independence vote and that only autonomy is on the table.An influx of people to the territory has boosted its population to more than 500 000, nearly all of whom live in its main towns. The territory boasts phosphate reserves and rich fishing grounds off its more than 1 000km Atlantic coast but its vast desert interior is virtually empty.At least 170 000 Saharawis live in desert refugee camps in neighbouring Algeria, the Polisario's staunchest backer.Two-thirds majority Algeria closed its border with Morocco in 1994 over the conflict and has never reopened it.Morocco will need a two-thirds majority among AU heads of state for its readmission to the bloc to be approved and there has been fierce lobbying by both sides.King Mohammed VI has been criss-crossing the continent lobbying for support since announcing the membership bid last year. Polisario leader Brahim Ghali was in Pretoria on Friday for talks with President Jacob Zuma, who said it was "unfathomable that Western Sahara... still remains colonised."South Africa and other southern states have long been staunch Polisario backers seeing in its struggle echoes of their own long wars for independence.Other regions of the continent are more divided, with Francophone states largely backing Morocco and Anglophone ones mainly supporting the Polisario.Several governments have changed sides more than once, freezing then restoring recognition of the SADR.