Western Sahara, an old conflict on the verge of explosion

Backed by neighbouring Algeria, the Polisario waged a guerrilla war until the UN brokered a ceasefire in 1991, with Morocco controlling about four-fifths of the territory

A dispute over Western Sahara threatens to result in a new round of conflict between Morocco and the Polisario Front independence movement.

Here are some facts about the territory, the dispute and the main players.

The Territory

The size of Britain, Western Sahara is sparsely populated with phosphate reserves and rich fishing grounds.

Morocco staked a claim to the territory while it was under Spanish colonial rule. At the same time, Sahrawi people living there formed the Polisario Front to push for independence.

When Spain left, Morocco annexed Western Sahara and encouraged thousands of Moroccans to settle there.

The Dispute

Backed by neighbouring Algeria, the Polisario waged a guerrilla war until the United Nations brokered a ceasefire in 1991, with Morocco controlling about four-fifths of the territory.

The truce included the promise of a referendum but that did not happen because of disagreements over how it should be carried out and who would be allowed to vote.

The new escalation is centred on Guerguerat, a crossing point between Western Sahara and Mauritania in a demilitarised region monitored by U.N. peacekeepers.

Polisario says the crossing, Morocco's main road link into West Africa, is illegal and the group's supporters have blocked it since Oct. 21.

Morocco sent troops on Friday to reopen the road to traffic and to build a new sand wall to prevent Polisario's fighters or civilian supporters from returning there.

Both have accused each other of breaking the ceasefire terms by sending armed forces into the area.

Morocco's Position

Morocco says it has centuries-old rights over the territory and that since annexation it has poured large sums of money into improving living conditions in Western Sahara.

Rabat has said that the most it can offer to Western Sahara is autonomy within Morocco.

Morocco has won praise for its improved human rights record since King Mohammed VI took power in 1999. But international rights groups say abuses continue, particularly in Western Sahara.

The Polisario Position

The Polisario set up a government in 1975 at Tindouf in neighbouring Algeria, winning admission to the predecessor organisation of the African Union but not recognition as a U.N. member state.

It has said it is ready to negotiate with Morocco on ways to hold a referendum offering a choice between independence, integration into Morocco, and self-governance.

Algeria's Position

Rabat's vision of autonomy is opposed by Algeria, Polisario's key ally. Thousands of Sahrawi refugees live in camps in the Algerian desert.

Western Sahara has been a bone of contention between Rabat and Algiers, and the border between them has been closed since the 1990s.

What About Diplomacy?

UN talks on Western Sahara's future between Morocco, the Polisario, Algeria and Mauritania have failed to reach agreement.

In October, the United Nations urged parties to work towards "a realistic, practicable and enduring political solutions... based on compromise". That language was seen as raising doubt over the prospects of a referendum.

Morocco has pushed to bring more countries into alignment with its position on Western Sahara. Over the past year, 16 African countries and the United Arab Emirates have opened consulates there.