The board of the UN nuclear watchdog on June 5 rebuked Iran for not cooperating fully with the agency, diplomats said, and called on Tehran to provide answers in a long-running investigation and reverse its decision to ban several experienced UN inspectors.

Iran’s Foreign Ministry issued a statement late in the night in response to the vote, saying it “strongly condemns” the action taken by the IAEA’s Board of Governors and describing the move as political.

The condemnation comes after the International Atomic Energy Agency reported a week ago that Iran had increased its uranium stockpile to weapons-grade levels, the latest in Tehran’s efforts to continue pressuring the international community.

The vote by the 35-member board at IAEA headquarters in Vienna is likely to further inflame tensions between the agency and Iran, which has previously reacted strongly to similar resolutions.

“The Islamic Republic of Iran considers the presentation and approval of this resolution a political and non-constructive action and a continuation of the past failed policies of some Western countries and an attempt to politically abuse international mechanisms against independent countries,” Iran’s Foreign Ministry statement said.

Twenty members voted in favour of the resolution, while Russia and China opposed it, 12 abstained and one did not vote, according to diplomats, who spoke on condition of anonymity to discuss the results of the closed-door vote. The resolution was introduced by France, Germany and Britain.

Censure resolutions passed by the IAEA board are not legally binding, but they send a strong political and diplomatic message.

The resolution, a draft of which was seen by The Associated Press, called on Tehran to implement a joint statement between Iran and the IAEA from March 2023. In that statement, Iran pledged to resolve issues around sites where inspectors have questions about possible undeclared nuclear activity, and allow the IAEA to “implement further appropriate verification and monitoring activities.”

Inspectors have said traces of processed uranium have been found at two sites near Tehran. The IAEA has urged Iran to provide “technically credible” answers about the origin and current location of the nuclear material so that it can be “in a position to provide assurances that Iran’s nuclear program is entirely peaceful.”

Although the number of sites the IAEA has questions about has dropped from four to two since 2019, these outstanding questions remain a continuing source of tension.

The IAEA identified these sites as Turkazabad and Varamin. The IAEA has said inspectors believe Iran used the Varamin site from 1999 to 2003 as a pilot project to process uranium ore and convert it into gas form. The IAEA said the buildings at the site were demolished in 2004.

Tehran says its programme is peaceful, though Western nations and the IAEA say Iran had an organised military nuclear programme by 2003.

The IAEA believes Turkazabad is the site where Iran took some of the material from Varamin during the demolition, although it has said this alone “cannot explain the presence of a wide variety of isotopically altered particles” found there.

In an apparent effort to increase pressure on Tehran, the resolution approved on Wednesday says that if Iran “continues to provide the necessary, full and frank cooperation” to resolve unanswered questions, IAEA Director General Rafael Mariano Grossi could be required to prepare a “comprehensive and updated assessment” on unresolved issues related to Iran’s nuclear program.

A statement by Iran’s foreign ministry in response to the condemnation did not include any threats to expand its nuclear program, as it broadcast in the days before the vote. In recent months, as tensions remain high in the region over the Israel-Hamas war, Iran has suggested it could potentially build nuclear weapons if it wanted to. The IAEA has warned that Iran now has enough highly enriched uranium to make “several” nuclear bombs, though it could take months to build one.

The IAEA board last condemned Iran in November 2022. Iran retaliated by beginning to enrich uranium up to 60% purity at its Fordo nuclear plant. Enriched uranium at 60% purity is just a small, technical step away from weapons-grade levels of 90%.

Iran responded to a previous resolution by removing IAEA cameras and monitoring equipment from its nuclear sites in June 2022.

In September, Iran blocked several experienced UN inspectors from monitoring the country’s nuclear program. Grossi said at the time that the decision was “a very serious setback” to the agency’s ability to do its job “at the best possible level.”

Under a 2015 deal with world powers, Tehran agreed to limit its enrichment of uranium to the level needed for nuclear power production in exchange for the lifting of economic sanctions. At the time, UN inspectors were tasked with monitoring the program.

However, tensions between Iran and the IAEA have steadily escalated since 2018, when then-President Donald Trump unilaterally withdrew the US from the nuclear deal. Since then, Iran has abandoned all limits imposed by the agreement on its programme and has rapidly increased enrichment.