Iran has threatened to limit UN inspectors' access to its nuclear facilities, even as it works to accelerate uranium enrichment in its latest breach of a 2015 landmark deal with world powers, prompting concern from European capitals. 

"We will probably impose limits on inspections, which means the International Atomic Energy Agency's (IAEA) surveillance on Iran's nuclear activities will be reduced," the newspaper Guardian quoted the spokesman for the Iranian parliament's national security committee, Hossein Naghavi-Hosseini, as saying on Wednesday.

"When the other party doesn't fulfill its commitments, there is no necessity for us to meet our part of commitments," he went on. 

"Europeans have not honored their part of the commitments and we have not seen any practical step taken by the other side."

"We will certainly take the fourth step of reducing commitments to the JCPOA," Naghavi-Hosseini concluded, referring to the Joint Comprehensive Plan of Action struck in July 2015 between Iran and six world powers – the U.S., China, Russia, the UK, France and Germany.

The landmark deal, under which Tehran agreed to limit enrichment activities in exchange for a lifting of sanctions, was meant to alleviate fears that Iran was developing nuclear weapons under the guise of a civilian program.

Read more: Explainer: What is the Iran nuclear deal?

But the Trump administration's withdrawal from the JCPOA in May 2018 and its reimposition of economic sanctions on Iran have reignited tensions and seen European allies scrambling to salvage what they can of the deal.

Hard hit by the sanctions, Tehran has been piling pressure on its European partners to ease trade and facilitate Iranian oil exports, increasingly stepping back from its 2015 commitments to achieve that.

Over the past few months, Iran has increased its stockpile of enriched uranium and refined it to a higher degree of purity than allowed under the JCPOA, according to the IAEA, the UN atomic watchdog charged with monitoring compliance. 

On Monday, President Hassan Rouhani also said that Iran was working on more advanced centrifuges for uranium enrichment, in violation of the 2015 deal. 

Reacting to the latest developments, France's foreign ministry expressed "deep concern" on Wednesday.

"Iran must refrain from entering a new and particularly troubling phase by adopting new measures that can only contribute to an escalation of tensions," the ministry said.

It also reiterated the so-called E3 powers' – France, the UK, Germany and the EU – commitment to the JCPOA and urged Tehran "to reconsider its decisions that run counter to that agreement, and to fully adhere to its obligations."

The next moves by Iran are expected to happen early next month.

"November 6 will be Iran's fourth violation," said a French diplomatic source, cited by Reuters. "Until now they have been political and symbolic with a limited impact on the breakout time, but the more they violate, the less choice and latitude they have that doesn't impact the breakout time."

The breakout time is the amount of time Iran would conceivably need to amass enough weapons-grade uranium to make a bomb.

"After November, the world doesn't end, but it becomes much harder to save the deal," the source said.