By Greg Barrow BBC United Nations correspondent

Under the plan, Western Sahara would be granted a limited form of autonomy from Morocco followed later by a referendum on independence from, or integration with Morocco.

US diplomats have circulated a draft resolution endorsing the plan, which was put forward earlier this year by UN special envoy and former US Secretary of State James Baker.

The decision by the independence movement to support the peace plan was the cause for mild celebration among some Security Council diplomats.

But others, who have grown used to the long and tortuous negotiations over this territory in north-west Africa, are more circumspect.

They welcome the flexibility shown by Polisario, but point out that Morocco - the other factor in this equation - has signalled no enthusiasm for the plan.

If the UN resolution is adopted, it would endorse the Baker plan and call on all parties to the dispute to work with the UN to ensure its implementation.

Some diplomats have voiced concern that this might appear to the Moroccans as an attempt to impose a solution on them without their agreement.

Morocco's supporters on the Security Council, who include the permanent member, France, are likely to defend their position should it appear to come under threat.

Even the most optimistic diplomats acknowledge that these latest developments may not be the breakthrough many have been hoping for.