Western Sahara's independence movement Polisario will vote in six months on whether to resume an armed struggle with Morocco over the desert territory, an official of the group said on Thursday.

"We will have a conference in six months to decide that," Mohamed Beissat told Reuters after a policy-making congress held in the Polisario-controlled outpost of Tifariti this week.

"The next conference will be in June or July."

The group said last week it was going to address the question of armed struggle at the Dec 14-20 gathering by voting on whether to resume war, continue negotiations or pursue some combination of the two.

Beissat said the congress had voted to proceed with negotiations for the next six months while at the same time improving the war readiness of Polisario armed forces.

"We have to strengthen our army so that it is ready for any decision that is eventually taken," said Beissat, who is also ambassador to Algeria of the self-proclaimed government for Western Sahara (SADR) declared by Polisario in 1976.

International peacekeepers have watched over the resource-rich territory of 260,000 people since 1991 when the U.N. brokered a ceasefire between the two sides to end a low-level guerrilla war.

Fighting broke out in 1975 when colonial power Spain withdrew from Western Sahara and Morocco annexed the northwest African territory rich in phosphates, fisheries and, potentially, oil.

Between 10,000 and 13,000 people were killed in the conflict, according to an estimate published in the 1990s by the Stockholm International Peace Research Institute.

The 1991 ceasefire accord promised a referendum on the fate of the territory but it never took place. Rabat now rules out such a vote and has French support for its proposal for self-rule under Moroccan sovereignty.