Morocco virtually annexed the northern two-thirds of Western Sahara (formerly Spanish Sahara) in 1976, and the rest of the territory in 1979, following Mauritania's withdrawal. A guerrilla war with the Polisario Front contesting Rabat's sovereignty ended in a 1991 UN-brokered cease-fire; a UN-organized referendum on final status has been repeatedly postponed. In April 2007, Morocco presented an autonomy plan for the territory to the UN, which the U.S. considers serious and credible. The Polisario also presented a plan to the UN in 2007. Since August 2007, representatives from the Government of Morocco and the Polisario Front have met three times to negotiate the status of Western Sahara, with a fourth round of negotiations planned for March 2008. Its languages are: Hassaniya Arabic and Moroccan Arabic