The U.N.-sponsored negotiations in Manhasset, near New York City, are the third round to tackle Africa's longest-running territorial dispute since the two sides submitted rival proposals for the resource-rich region last April.

Morocco took control of most of Western Sahara in 1975 when colonial power Spain withdrew, prompting a guerrilla war for independence that lasted until 1991 when the United Nations brokered a cease-fire and sent in peacekeepers.

Moroccan and Polisario negotiators were to have dinner together at Manhasset on Monday evening before conducting the talks on Tuesday and Wednesday. However, neither they nor U.N. officials saw much likelihood of a major breakthrough.

Polisario, which is backed by Morocco's regional rival Algeria, said last month war may restart if the talks fail to reach accord on whether Western Sahara should be independent or an autonomous region of Morocco.

"It will be the last opportunity Polisario offers Morocco," Polisario's envoy to Algeria Mohamed Yasslim told Algeria's main Arabic-language al Khabar daily in a recent interview.

"Preparations for war are afoot at all levels."

A statement issued by Ban's spokeswoman, Michele Montas, said the U.N. chief "recognizes that it will take both time and patience to negotiate a mutually acceptable solution ... He appeals to the parties ... to begin moving into a more intensive and substantive phase of discussions."

HOPING FOR PROGRESS

Ban, who complained last year that the two sides were not really negotiating, declined comment on the Polisario threat at a news conference on Monday, but said: "I hope that this time they will be able to make good progress in this issue."

But another U.N. official, who asked not to be identified, told Reuters: "I don't want to give you the impression that a big outcome is expected."

Analysts say war is unlikely for now as Polisario relies heavily on Algeria, which has no wish to increase regional tensions.

North African countries are under pressure to settle their differences in order to better deal with growing violence by al Qaeda-linked radical Islamists. Algeria has suffered a series of deadly suicide bombings since early last year, the latest on Dec. 11 killing 37 people, including 17 U.N. staff in Algiers.

The desert territory of 260,000 on Africa's Atlantic coast holds phosphates, rich fisheries and potentially offshore oil.

Rabat is trying to convince Polisario to accept its plan for Western Sahara to be an autonomous part of Morocco. Polisario proposes a referendum among ethnic Sahrawis that includes an option of independence.

Moroccan officials warned against over-optimism. "We do not expect a breakthrough from the upcoming talks," one said.

In New York, Polisario U.N. representative Ahmed Boukhari also played down expectations. "Unfortunately, we hear Morocco is not going to change its position," he said.

Rabat and Polisario have lined up the same officials who took part in previous talks in June and August that ended with no tangible outcome, prompting the U.N. Security Council to urge them to put more effort into the negotiations.

No state recognizes Morocco's rule over Western Sahara but the Security Council is divided. Some non-aligned states back Polisario, but France and the United States support Rabat.