Not surprised Iran going to violate nuclear deal: US defence secretary Mark Esper

US defense secretary Mark Esper said on Saturday he was "not surprised" Iran had turned on advanced centrifuges to increase uranium stockpiles, a further breach of the 2015 nuclear deal which Washington pulled out of last year.

"I'm not surprised that Iran has announced that it's going to violate the JCPOA," Esper said in Paris, using the official name of the accord signed in Vienna four years ago.

"They had been violating it, they had violated the nuclear non-proliferation treaty for many years, so it's no surprise that the Iranians are going to pursue what the Iranians have always intended to pursue," he added, following talks with his French counterpart Florence Parly.

Esper was in France after visits to London and Stuttgart, Germany, to meet with NATO allies since taking up his post in July.

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Parly reiterated France's calls for Tehran to "respect the Vienna accord", adding, "we will continue with all our diplomatic efforts in this direction. We have to continue."

France and other EU nations have been trying to ease tensions in the Gulf region since President Donald Trump abandoned the nuclear deal and re-imposed sanctions that have hit the Iranian economy hard.

President Emmanuel Macron has overseen recent talks between French and Iranian officials, and even secured a potential opening with Trump at last month's G7 summit, when he said he would be willing to meet with Iran's President Hassan Rouhani.

Esper said he had "productive discussions" with Parly, though neither indicated any progress had been made on de-escalating the conflict.

They also agreed to disagree on the US's new "maritime security mission" in the Gulf, aimed at ensuring open passage for vessels through the Strait of Hormuz after a series of incidents, including ship seizures by Iranian forces.

France has declined to join the US initiative and instead sought out like-minded partners for its own surveillance of the strategic waterway.

"The goal is to rally as many partners and means of surveillance as possible to improve security in the Gulf, and there's absolutely no competition between these initiatives," Parly said.

Esper said the US effort "is about deterring bad behaviour."

"Obviously our preference is that all countries join underneath this broader umbrella," he said.

"But the key thing is that we all work together to defend those common values, those common rights, that we have set up in the wake of World War-II and defend those around the world, whether it's from Iran trying to violate them, or it's China in the South China Sea."