By Subir Bhaumik BBC correspondent in Calcutta

Foreign Minister Thinley says force will be the only option if talks fail

Bhutan says it will make one more effort to persuade separatist rebels from the Indian state of Assam to leave the kingdom.

Two Assam separatist groups have maintained a number of bases in southern Bhutan for well over a decade.

They use them to attack targets inside Assam.

A deadline set by Bhutanese Government for the rebels to leave expired on Monday.

Indian pressure on Bhutan to push the rebels out has increased.

Fresh mandate

Bhutanese Foreign Minister Jigme Thinley told the BBC's World Today Programme that his government wants to make one last effort to persuade the leaders of the United Liberation Front of Assam (ULFA) and the National Democratic Front of Bodoland (NDFB) to leave the kingdom.

He said his government wanted to seek a fresh mandate from the national assembly for holding one final round of talks with the rebel leaders - failing which, he said, Bhutan's options would narrow down to use of force.

Indian forces have been fighting the rebels for two decades

He said Bhutan will deal with this problem through its own resources and would not call in the Indian army to push the rebels out.

Mr Thinley said the rebel presence in southern Bhutan was turning out to be a major problem.

Bhutanese officials say that the ULFA leaders, during their talks with Bhutan, have said they could not leave the kingdom because of the heavy presence of Indian security forces on its borders with Assam.

Analysts say Bhutan is buying time to prepare for a military offensive against the rebels if the tough posturing fails to provide results.