French President Francois Hollande said on Monday his country would stand firm on its demand that Tehran vow not to pursue nuclear weapons ahead of fresh international negotiations.

"If there is no clear statement from Iran on giving up nuclear weapons, there will be no agreement," Hollande said on France Inter radio.

"France will not yield on that point. It will remain absolutely firm," he added.

Western countries fear Iran is seeking to build nuclear weapons, which Tehran has strongly denied.

Iran and the "P5+1" group of nations -- the US, Britain, France, Russia, China and Germany -- are due to resume talks in January.

A temporary agreement was signed in November 2013, with Tehran accepting strict constraints on its nuclear programme in exchange for a lifting of sanctions.

But two subsequent deadlines to make the deal permanent have had to be extended. A fresh deadline of June 30 has been set.

The talks have been complicated by the conflicts in Iraq and Syria, with the West finding itself on the same side as Iran in combating the Islamic State (IS) jihadist group.

Hollande accepted that Iran is "a partner in finding stability in Iraq and Syria", but France has been keen to separate that issue from the nuclear talks.

"If Iran wishes to fight against Daesh (an alternative name for IS), it is because the group represents a threat to its interests," said Defence Minister Jean-Yves Le Drian last month.

"Hoping that support from Iran against Daesh can be exchanged for us ignoring Tehran's violations on non-proliferation issues would be a profound error."