The report by the International Atomic Energy Agency said Iran had sharply increased its stockpile of uranium enriched to up to 60 percent, close to the roughly 90 percent level needed for atomic weapons.

Iran's total amount of enriched uranium now exceeds 45 times the limit authorised by a landmark 2015 agreement with world powers, and is estimated at 9,247.6 kilograms, according to the confidential IAEA report seen by AFP.

Iranian Foreign Minister Abbas Araghchi said in a statement he had told IAEA chief Rafael Grossi in a phone call that "Iran will respond to any inappropriate action by the European parties" to the 2015 agreement, referring to Britain, France and Germany.

The European trio have warned they could reimpose sanctions if they deemed Iran's nuclear programme a threat to the continent's security.

Araghchi urged Grossi in their Saturday call to stop "parties from exploiting" the nuclear watchdog report "to advance their political objectives", according to the statement.

The IAEA Board of Governors is set to review Iran's nuclear activities in its upcoming quarterly meeting in Vienna starting June 9.

Iran rejected the IAEA report, the latest move in years-long efforts to restrict its nuclear activities over fears that it is seeking to develop nuclear weapons.

The Islamic republic has denied seeking nuclear arms and says it needs the uranium for civilian power production.

The report was leaked as Iran and the United States have been engaged in negotiations towards a new nuclear deal, after Washington had unilaterally abandoned the agreement between Tehran and world powers in 2018, during President Donald Trump's first term.

- US proposal -

Araghchi said on Saturday that he had received "elements" of a US proposal for a potential nuclear deal following five rounds of talks mediated by Oman.

Iran would respond "in line with the principles, national interests and rights" of its people, Araghchi added in a post on X.

White House press secretary Karoline Leavitt said that the United States "has sent a detailed and acceptable proposal to the Iranian regime, and it's in their best interest to accept it", the New York Times reported.

The proposal was described as a series of bullet points rather than a full draft, according to the New York Times, citing officials familiar with the diplomatic exchanges.

It calls on Iran to stop all enrichment of uranium and proposes creating a regional grouping to produce nuclear power, which would include Iran, Saudi Arabia and other Arab states, as well as the United States.

Trump adopted a "maximum pressure" policy against Tehran after withdrawing from the 2015 agreement and reimposed sweeping sanctions which the deal had lifted in return for UN-monitored restrictions on Iran's nuclear activities.

Iran has ramped up its nuclear activities since the collapse of the deal, and is now enriching uranium to 60 percent -- far above the deal's 3.67 percent cap but below the 90 percent needed for weapons-grade material.

The 2015 deal provides for the possibility of UN sanctions being reimposed through a mechanism called "snapback" if Iran fails to fulfil its commitments, an option that expires in October.

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THE NEW YORK TIMES COMPANY