(Bloomberg) -- The United Nations’ atomic watchdog reported that despite the growing presence of inspectors in Iran last year, its understanding of the Persian Gulf nation’s nuclear ambitions deteriorated amid spiking regional tensions. 

The International Atomic Energy Agency circulated its annual nuclear-monitoring assessment among diplomats preparing to convene a key meeting in Vienna next month. Iran is facing mounting pressure to boost cooperation with UN inspectors, or face diplomatic censure followed by a potential referral to the UN Security Council. 

“While regular inspection work has continued, there has been little progress in resolving the outstanding safeguards issues,” IAEA Director General Rafael Mariano Grossi wrote in the restricted 112-page report seen by Bloomberg. 

“Unless and until Iran clarifies these outstanding issues, the agency is unable to provide assurance about the exclusively peaceful nature of Iran’s nuclear program,” he said.

Even as inspections increased 8% last year and remain well above the level experienced before Iran’s defunct 2015 agreement with world powers, the IAEA said that its understanding of certain activities has been lost entirely.

“The agency has lost continuity of knowledge in relation to the production and inventory of centrifuges, rotors and bellows, heavy water and uranium ore concentrate,” wrote Grossi, who last week visited Iran for high-level talks meant to increase cooperation. 

This week’s so-called Safeguards Implementation Report is one of two key IAEA documents being prepared ahead of a June 3 meeting in the Austrian capital. Monitors are still drafting a quarterly safeguards report informing diplomats about the state of their investigations in Iran and updating envoys on the size of Iran’s growing uranium stockpile. 

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, where sanctions on the Islamic Republic may be renewed. Some European countries already wanted to dial up the pressure in March. 

The IAEA’s assessment of Iran underscores the limitations of nuclear safeguards. While inspectors report gram-level changes in Iran’s uranium inventory they’re unable to gage intent because they’re frozen out of facilities where declared fuel isn’t present. Some diplomats are concerned that Iran may be hiding sites with machinery or uranium ore. 

Compounding the unease, a series of comments by past and present Iranian officials have suggested the country could shift its nuclear doctrine and build a weapon. Tit-for-tat missile strikes between Israel and Iran last month are adding urgency to the IAEA’s years-long probe into the provenance of uranium sampled at uncleared locations in Iran. 

The IAEA also reported in its annual safeguards review that:

  • Inspectors wrote that their “overall security situation” in some states continued to be a concern. The IAEA had to temporarily pause inspections last month after Iran closed facilities because of anticipated military strikes with Israel.
  • Even when inspectors aren’t on the ground, the IAEA is tracking nuclear activities with remote-sensing imagery, including online streaming rendered by satellites. Inspectors procured some 1,768 satellite images of sites in 52 countries last year.
  • The agency is developing artificial tools to sift through and collect open-source intelligence to help prioritize investigations and new inquiries.
  • IAEA inspectors accounted for fissile material needed to make almost 236,000 nuclear weapons at 724 sites worldwide. Iran’s current uranium stockpile could fuel a handful of warheads should a weaponization decision be taken.

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