Le Drian's comments, to the National Assembly's foreign affairs committee, came against a background of Iranian moves to disregard elements of the deal and escalating tension in the Gulf region.

"Every two months there is another notch (from Iran) to the extent that we are wondering today, and I say very clearly, about the implementation of the dispute resolution mechanism in the treaty," he told the lawmakers.

"Given the succession of actions taken by the Iranian authorities, who are progressively at odds with the the contents of the JCPOA (the nuclear deal), the question comes up," he added.

Since May, Tehran has made a number of moves that have raised concerns in the West that it is moving towards abandoning the agreed limits to its nuclear activities.

The 2015 Joint Comprehensive Plan of Action (JCPOA) set out the terms turns under which Iran would restrict its nuclear programme to civilian use in exchange for the lifting of western sanctions.

When US President Donald Trump pulled out of the agreement in 2018, reimposing heavy sanctions, Iran began to breach some parts of the deal in response.

Le Drian, in his comments to the committee, appeared pessimistic that France's efforts to save the agreement would succeed.

- French overtures ignored -

French President Emmanuel Macron has been trying to organised a meeting between Trump and Iranian President Hassan Rohani, but so far without success.

"The efforts at de-escalation that we have attempted, that the President of the Republic has attempted on several occasions, have not come to anything for a whole series of reasons," he said.

Iran's detention in June of two French researchers, anthropologists Fariba Adelkah and Roland Marchal, had not helped matters, he added. Nor had Iran's activities in the region.

Since May, tensions in the Gulf have escalated following a string of attacks on oil tankers that the United States and its allies blamed on Tehran. The Islamic republic denies the charges.

Iran, however, admitted to shooting down a US drone in June for allegedly flying over its territorial waters. Washington insisted the aircraft was in international airspace.

European efforts to shield Iran from the effects of US sanctions by finding ways to continue trade with the Islamic republic have borne little fruit, much to Tehran's frustration.

The EU is growing increasingly concerned at Tehran's decision to row back on its commitments, notably by stepping up uranium enrichment.

Earlier this month Germany warned that the dispute resolution mechanism in the deal could be triggered if Iran continued down this path.

This covers various stages that could take several months to unfold, but the issue could eventually end up before the UN Security Council, who could decide to reimpose sanctions.