– Iran on Monday set a 10-day countdown for world powers to fulfil their commitments under a nuclear deal abandoned by the United States or else it will surpass its uranium stockpile limit.
The US responded by urging the international community not to give in to Iranian "nuclear extortion", while the UN and European states called for cool heads.
UN Secretary-General Antonio Guterres urged Iran to continue to abide by the 2015 nuclear deal and for all parties to refrain from steps that may escalate tensions in the Middle East.
"Today the countdown to pass the 300 kilograms reserve of enriched uranium has started and in 10 days time… we will pass this limit," said Iran\’s atomic energy organisation spokesman Behrouz Kamalvandi.
The move "will be reversed once other parties live up to their commitments", he added, speaking from the Arak nuclear plant, southwest of Tehran.
US State Department spokeswoman Morgan Ortagus said the world "should not yield to nuclear extortion".
"It\’s unfortunate that they\’ve made this announcement today but I said earlier it doesn\’t surprise anybody," she said.
"We continue to call on the Iranian regime to abide by their commitments to the international community."
French President Emmanuel Macron encouraged Iran to be "patient and responsible" at a time when the US is blaming Iran for attacks on tankers in the Gulf of Oman.
– \’Dissuade Iran\’ –
Israel\’s Prime Minister Benjamin Netanyahu called on the international community to immediately hit Iran with "snapback sanctions" should it violate the deal by surpassing the uranium stockpile limit set in the deal.
On May 8, President Hassan Rouhani said Iran would stop observing restrictions on its stocks of enriched uranium and heavy water agreed under the nuclear deal.
Rouhani said the move was in retaliation for the unilateral US withdrawal from the accord last year, which saw Washington impose tough economic sanctions on Tehran.
Tensions between Tehran and Washington have escalated ever since, with the US bolstering its military presence in the region and blacklisting Iran\’s elite Revolutionary Guards as a terrorist organisation.
The US has also blamed Iran for last week\’s attacks on two tankers in the Gulf of Oman, a charge Tehran has denied as "baseless".
Iran has threatened to go even further in scaling down nuclear commitments by July 8 unless remaining partners to the deal — Britain, China, France, Germany and Russia — help it circumvent US sanctions and especially enable it to sell its oil.
"The current situation is sensitive" and there is still time for the deal\’s partners to save this agreement, Rouhani told the French ambassador to Tehran, Philippe Thiebaud, on Monday.
Speaking in Paris, Macron said he regretted Tehran\’s latest announcements.
"We strongly encourage Iran to behave in a way that is patient and responsible," he said.
Any kind of escalation "is damaging to the interests of the Iranians themselves and also to the international community", he added.
"So we will do everything with our partners to dissuade Iran from this (surpassing the limit)," he said.
German Foreign Minister Heiko Maas rejected the Iranian ultimatum and insisted Tehran stick to its commitments under the deal.
A spokesman for the British government echoed the call, saying the E3 — the European signatories to the deal — has "consistently made clear that there can be no reduction in compliance".
– \’Save the deal\’ –
Under the agreement, Iran pledged to reduce its nuclear capacities for several years and allow international inspectors inside the country to monitor its activities in return for relief from international sanctions.
The deal set a limit on the number of uranium-enriching centrifuges, and restricted its right to enrich uranium to no higher than 3.67 percent, well below weapons-grade levels of around 90 percent.
It also called on Iran to export enriched uranium and heavy water to ensure the country\’s reserves would stay within the production ceiling set by the agreement, yet recent US restrictions have made such exports virtually impossible.
According to Rouhani, the ultimatum he issued last month was intended to "save the (deal), not destroy it".
The three European parties to the accord created a trade mechanism meant to bypass US sanctions, but their attempt was dismissed by Iran\’s supreme leader Ayatollah Ali Khamenei as a "bitter joke".
The spokesman for Iran\’s atomic energy organisation warned further steps could be taken if world powers do not step up to help the country.
"They range from going to 3.68 percent to any other percent according to the country\’s needs," said Kamalvandi.
Authorities were still debating whether to "redesign or revive" the Arak reactor, he added.
Uranium enriched to much higher levels than Iran\’s current stocks can be used as the fissile core of a nuclear weapon, while heavy water is a source of plutonium, which can be used as an alternative way to produce a warhead.