(Adds death toll estimate para 12)

By William Maclean

ALGIERS, Dec 16 (Reuters) - The Western Sahara independence movement Polisario will vote on Tuesday on whether to revive its armed struggle against Morocco over the desert territory, a Polisario official said on Sunday.

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

But Mhamed Khadad said Polisario officials who met on Saturday at a strategy conference at the Polisario-controlled outpost of Tifariti had considered a resumption of armed struggle, continued negotiations or a mix of the two.

"We had a big debate yesterday over negotiations," Khadad, a senior Polisario official who is also the conference spokesman, said by telephone from Tifariti.

"The military people said 'We can't keep negotiating idenfinitely. We need to assess the situation ... We should propose resuming armed struggle."

"Others said 'No, No, we should continue negotiating because we have a third round of talks just coming up in January."

"We will vote on this on the 18th at the end of the conference," Khadad said.

MIXED STRATEGY

Khadad went on: "And then there was a third line, to the effect that 'we can't negotiate indefinitely, maybe we should have a followup conference to make a decision in 6, 12 or 18 months'."

Polisario officials have said the national secretariat will recommend a mixed strategy to the congress of more than 1,500 delegates -- start preparations for the resumption of war while pursuing negotiations at the same time.

A vote in favour of that approach would be the first time preparation for war has been part of Polisario strategy on the territory of 260,000 since the truce was agreed.

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.

A rival Polisario plan proposes a referendum with independence as one option. Two rounds of U.N.-sponsored peace talks in New York this year made no progress on breaking the stalemate. A third round is to be held Jan. 7-9.

No country officially recognises Morocco's rule over Western Sahara but the U.N. Security Council is divided over a solution, with some nonaligned states supporting Polisario but France and the United States leaning towards Morocco.

Morocco says independence cannot work as ethnic Sahrawis live in four countries and a referendum is impossible to stage.

Polisario is widely considered the weaker party militarily. A 1,500 km (940 mile) sand wall separates a 100,000-strong Moroccan army from about 12,000 Polisario soldiers. (Editing by Richard Balmforth)

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