Iran has removed “basically all” of the additional monitoring equipment installed under the 2015 nuclear deal, the chief of the UN's nuclear watchdog said on Thursday.
Rafael Grossi, the director general of the International Atomic Energy Agency, said Iran had so far removed 27 surveillance cameras at its nuclear sites.
He said the move was a “serious challenge” to the agency's work in the country.
“What we have been informed is that 27 cameras … are being removed in Iran,” Mr Grossi said.
“So this, of course, poses a serious challenge to our ability to continue working there.”
The latest move from Iran comes after the agency's board of governors officially rebuked Tehran on Wednesday for having nuclear materials at undeclared sites.
The row has escalated in recent months, with talks over resurrecting the 2015 deal in Vienna reaching a dead end after a year of on-and-off meetings.
The agency has said the responses given by Iranian officials to questions about the materials seem to lack credibility.
US Secretary of State Antony Blinken said on Thursday that Iran's latest “provocations” around its nuclear programme risk a “deepening” crisis and further economic and political isolation for Tehran.
“Unfortunately, Iran's initial response to the board’s action has not been to address the lack of co-operation and transparency that prompted a negative report from the IAEA director general and such strong concern in the board, but instead to threaten further nuclear provocations and further reductions of transparency,” Mr Blinken said in a statement.
“Such steps would be counterproductive and would further complicate our efforts to return to full implementation of” the nuclear deal.
“The only outcome of such a path will be a deepening nuclear crisis and further economic and political isolation for Iran. We continue to press Iran to choose diplomacy and de-escalation instead,” he said.
The UK, France and Germany issued a joint statement on the current position of the nuclear deal, saying: “There has been a viable deal on the table since March 2022, which would return Iran to compliance with its [Joint Comprehensive Plan of Action] commitments and the US to the deal.
“We regret that Iran has not seized the diplomatic opportunity to conclude the deal. We urge it to do so now.”
The countries blasted Iran for installing additional advanced centrifuges and telling the agency it would end all deal-related transparency measures.
“This jeopardises the ability of the [agency] to restore continuity of knowledge on key parts of the Iranian nuclear programme, including on the production of centrifuges,” the joint statement said.
“We condemn these steps and that it is responding to concerns expressed by the IAEA board of governors — in a resolution adopted with overwhelming support — by announcing steps to even further decrease co-operation with the IAEA.”
The statement said Iran's actions only aggravate the situation and complicate efforts to restore the deal fully while also casting doubt on Tehran's commitment to a successful outcome.
“We urge Iran to resume application of the additional protocol and of all JCPOA-related monitoring and verification measures, cease its nuclear escalation and urgently conclude the deal currently on the table to restore the JCPOA, while this is still possible,” the statement said.
The Atomic Energy Organisation of Iran, which runs its nuclear programme, published video on Thursday that it said showed its workers turning off regular and backup battery power for two agency cameras on Wednesday.
Iran said it also planned to install two new cascades of advanced centrifuges that would allow it to enrich more uranium quickly, the IAEA said.
The decision to add the two IR-6 centrifuges cascades at its underground Natanz site comes as countries at an agency meeting in Vienna voted to censure Iran.