Britain, France and Germany on Thursday launched a 30-day process to reimpose UN sanctions on Iran over its disputed nuclear programme, two months after Israel and the United States bombed Iran.

Hours after the announcement, Iran's foreign minister Abbas Araqchi, said the country is ready to resume "fair" nuclear negotiations if the West shows goodwill.

"Araqchi reaffirmed Iran's readiness to resume fair and balanced diplomatic negotiations, on the condition that the other parties show seriousness and goodwill and avoid actions that harm the chances of success," he said in a letter sent to European Union foreign policy chief Kaja Kallas.

The three powers, known as the E3, launched the so-called "snapback mechanism" over fears that they would otherwise lose the prerogative in mid-October to restore sanctions on Tehran that were lifted under a 2015 nuclear accord with world powers.

French Foreign Minister Jean-Noel Barrot said the decision did not signal the end of diplomacy. His German counterpart Johann Wadephul urged Iran to now fully cooperate with the UN nuclear watchdog agency and commit to direct talks with the United States over the next month.

The UN Security Council is due to meet behind closed doors on Friday at the request of the E3 to discuss the snapback move against the Islamic Republic, diplomats said.

Iran and the E3 have held several rounds of talks since Israel and the US bombed its nuclear installations in mid-June, aiming to agree to defer the snapback mechanism. But the E3 deemed that talks in Geneva on Tuesday did not yield sufficiently tangible commitments from Iran.

The E3 acted on Thursday over accusations that Iran has violated the 2015 deal that aimed to prevent it developing a nuclear weapons capability in return for a lifting of international sanctions.

The E3, along with Russia, China and the United States, were party to that accord.

US President Donald Trump pulled Washington out of that accord in 2018 during his first term, calling the deal one-sided in Iran's favour. His second administration held fruitless indirect negotiations earlier this year with Tehran.

US Secretary of State Marco Rubio welcomed the E3 move, saying the Europeans had laid out a clear case of Tehran's “significant non-performance" on its nuclear commitments.

Rubio said the United States remained available for direct engagement with Iran "in furtherance of a peaceful, enduring resolution to the Iran nuclear issue".

But Russia's deputy UN Ambassador Dmitry Polyanskiy said the process to reimpose sanctions should not be acted on by the Security Council because it has no legal bearing.

The E3 said they hoped Iran would engage by the end of September to provide commitments over its nuclear programme sufficient for them to defer concrete action.

"The E3 are committed to using every diplomatic tool available to ensure Iran never develops a nuclear weapon. That includes our decision to trigger the 'snapback' mechanism today through this notification," they said in a letter sent to the UN Security Council and seen by Reuters.

"The E3's commitment to a diplomatic solution nonetheless remains steadfast. The E3 will fully make use of the 30-day period following the notification in order to resolve the issue giving rise to the notification."

The UN process takes 30 days before sanctions that would hit Iran's financial, banking, hydrocarbons and defence sectors are restored. (Reuters)