The UN Security Council is considering a draft resolution to approve the creation of a 12,600-strong UN peacekeeping force in Mali starting on July 1, which would be able to request the support of French troops if needed to combat rebel threats.

Experts from the 15 Security Council members are due to meet on Tuesday to discuss the resolution, drafted by France and obtained by Reuters news agency, which would authorise peacekeepers and French troops to use "all necessary means" to protect civilians and stabilise key cities, especially in Mali's desert north.

The Security Council hopes to adopt the resolution, which may be revised during negotiations, by the end of April.

A senior UN official, speaking on the condition of anonymity, said the operation would be the fourth largest UN peacekeeping force and cost up to $800m annually.

France, aided by some 2,000 troops from Chad, began a military offencive in January to drive out fighters, who had hijacked a revolt by Mali's Tuareg rebels and seized two-thirds of the West African country.

France has started withdrawing its 4,000-strong force and plans to have just 1,000 by the end of the year. Chad said on Sunday it would also withdraw from Mali after helping the French drive rebels from northern towns, mountains and deserts.

Syria had said Mali's north was in danger of becoming a springboard for extremist attacks on the region and the West.

"French forces will be ready to provide support [to the peacekeepers]," said a senior Security Council diplomat, speaking on the condition of anonymity.

"You can't ask the blue helmets [peacekeepers] to engage in counterterrorism."

The draft Security Council resolution proposes that a UN peacekeeping force - to be known as MINUSMA - take over authority on July 1 from a UN-backed African force in Mali that has been deployed there to take over from the French forces.