European powers urged Iran on Tuesday to reverse its move to increase uranium enrichment, as a French envoy was due in Tehran to boost efforts to save a landmark 2015 nuclear deal.
The accord between Iran and world powers promised sanctions relief, economic benefits and an end to international isolation of the Islamic republic in return for stringent curbs on its nuclear programme.
But Tehran says it has lost patience with perceived inaction by European countries more than a year after president Donald Trump pulled the United States out of the agreement.
The European parties to the deal along with the EU's diplomatic chief on Tuesday called on Tehran to reverse breaches of the agreement.
"The foreign ministers of France, Germany, and the United Kingdom and the (EU) High Representative express deep concern that Iran is pursuing activities inconsistent with its commitments under the Joint Comprehensive Plan of Action (JCPoA)," they said in a statement, using the deal's official name.
"It must act accordingly by reversing these activities and returning to full JCPoA compliance without delay."
According to the International Atomic Energy Agency (IAEA), tasked with inspections, while Iran consistently lived up to its commitments under the deal until recently, it is now in breach of two of them.
French president Emmanuel Macron sent his top diplomatic advisor to Tehran after Iran announced on Monday it had passed 4.5 per cent uranium enrichment -- above the 3.67 per cent limit under the agreement though still far below the 90 per cent necessary for military purposes.
Emmanuel Bonne is due to visit until Wednesday but details of his schedule were not fully clear.
A meeting with Rear-Admiral Ali Shamkhani, secretary of Iran's Supreme National Security Council, is planned for Wednesday morning.
Bonne is "to piece together a deescalation" strategy, the French presidency's office said.
The 2015 deal had been described as a triumph of diplomacy against unilateralism and a major step to counter proliferation.
But after the US withdrew in May 2018 and reimposed stinging sanctions on Iran, especially on its banking and oil sectors, the future of the accord became uncertain.
As the Iranian economy went into free-fall, Tehran demanded that the other parties to the deal, especially France, Germany and Britain, deliver the promised economic benefits and help it bypass US sanctions.
However, it gradually became clear that this was no simple task, and Iran -- whose economy is heavily dependent on oil sales -- changed tack and said it would reshape its policy of "strategic patience".
In May, a year after Trump's withdrawal, president Hassan Rouhani said that Iran would roll back its commitments under the deal in stages every 60 days in an effort to force the other parties to deliver on their side of the bargain.
As tensions rose the United States dispatched a naval carrier, bombers and extra troops to the region to counter perceived threats from Iran.
'US, Europe deceiving us'
Last month Trump said he had called off a retaliatory military strike against Iran at the last minute after Tehran shot down a US drone that it said had crossed into its airspace, a claim denied by Washington.
The UN nuclear watchdog confirmed this month that Iran has exceeded a 300-kilogramme limit on enriched uranium reserves, another cap that was imposed by the deal.
Macron on Saturday held an hour-long conversation with Rouhani in which he said he wanted to "explore the conditions for a resumption of dialogue between all parties".
On Monday the White House confirmed that Macron and Trump had talked about the standoff.
The two leaders "discussed ongoing efforts to ensure that Iran does not obtain a nuclear weapon and to end Iran's destabilising behaviour in the Middle East," the White House said in a statement.
While immensely popular to begin with, the nuclear deal has now lost some of its appeal among supporters in Iran.
"The US and the European countries are deceiving us... We wasted six years investing in our relationship with Europe," Majidi, a salesman in Tehran, told AFP, adding that the best option now is to pull out of the deal immediately.