(Bloomberg) — Iran increased its stockpile of near bomb-grade uranium, a move that could flame tensions across the wider Middle East as Tehran prepares to hold presidential elections next month.

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It’s the first nuclear-safeguards assessment since Iran’s president and foreign minister died in a helicopter crash just days after top officials from the United Nations’ atomic watchdog traveled to the country to secure greater cooperation in their monitoring efforts.

International Atomic Energy Agency inspectors verified on Monday that Iran’s stockpile of highly enriched uranium rose 17% over the last three months, according to a nine-page, restricted report circulated among diplomats and seen by Bloomberg. That’s enough uranium to fuel several warheads, should Iran make a political decision to pursue weapons.

“Further public statements made in Iran during this reporting period regarding its technical capabilities to produce nuclear weapons and possible changes to Iran’s nuclear doctrine only increase concerns about the correctness and completeness of Iran’s safeguards declarations,” IAEA Director General Rafael Mariano Grossi said in the report.

Recent tit-for-tat missile strikes between Israel and Iran have added urgency to the IAEA’s years-long search to uncover the scope of Tehran’s nuclear ambitions. While the IAEA carries out daily inspections of declared atomic facilities, suspicions linger over whether Iranian engineers could be concealing work used for military purposes. Tehran has blocked the agency’s investigation into uranium detected at undeclared locations.

While Iran insists it isn’t looking to produce nuclear weapons, international mistrust prompted a negotiated compromise in 2015 that restricted the country’s atomic activities in exchange for sanctions relief. Recent statements by current and former Iranian officials that the country could revisit its nuclear doctrine — and potentially build a weapon — prompted Grossi to renew attempts at diplomacy through his visit earlier this month.

Read more: Iran’s Nuclear Saber Rattling Raises More Alarm at UN Watchdog

The US issued an ultimatum to Iran at the IAEA’s last meeting: cooperate or face censure, which could lead to a referral to the UN Security Council and the renewal of sanctions against the Islamic Republic. Some European countries already wanted to dial up the pressure in March. The IAEA’s board convenes again on June 3 in the Austrian capital.

Iran’s stockpile of uranium enriched to 60% levels of purity — a level indistinguishable from weapons-grade fuel — rose to 142 kilograms (313 pounds) from 121.5 kilograms March, the IAEA inspectors concluded. Inventories of 20%-enriched fuel grew to 751 kilograms from 712.2 kilograms.

IAEA inspectors reported that Iran continues to stonewall a probe into uranium particles detected at undeclared locations.

“There has been no progress in the past year,” Grossi told diplomats. Iran informed IAEA representatives visiting Tehran on May 20 that due to the president and foreign minister’s deaths, “it was no longer appropriate” to hold substantive discussions, and the quest for a solution would need to wait for an undetermined time, read a second eight-page report circulated Monday.

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