Iran increased its stockpile of 60 percent enriched uranium by 133.8 kilograms, or 3.2 significant quantities, since February 2025, according to an unreleased International Atomic Energy Agency (IAEA) report.[1] Iran has enough 60 percent enriched uranium, if enriched further, to produce nearly 10 nuclear weapons. The Associated Press reported on May 31 that Iran possesses 408.6 kilograms of uranium enriched up to 60 percent, or 9.8 significant quantities, as of May 17.[2] A significant quantity is the “approximate amount of nuclear material for which the possibility of manufacturing a nuclear explosive device cannot be excluded.”[3] Iran had 274.8 kilograms of uranium enriched up to 60 percent, or 6.6 significant quantities, in February 2025, by comparison. The IAEA report added that Iran's total stockpile of enriched uranium is 9,247.6 kilograms, which marks a 953.2-kilogram increase since February 2025.[4] The IAEA report does not provide a month-to-month breakdown of Iran's uranium enrichment activity. It is therefore unclear whether Iranian uranium enrichment increased, decreased, or remained the same following the start of the US-Iran nuclear negotiations on April 12. Iran has previously increased its stockpile of enriched uranium to try to gain leverage in negotiations.[5] It is unclear, however, why Iran would pursue rapid enrichment amid the current US-Iran negotiations and potentially increase the risk of snapback sanctions or potential US or Israeli strikes on Iran. The IAEA report comes as Iran has taken other measures to expand its nuclear program in recent months. Iran has installed new cascades of advanced centrifuges at Natanz and Fordow. Iran has also conducted metallurgical testing and computer simulations that could support the production of a nuclear weapon.[6]
The IAEA separately published a comprehensive report on May 31 that states that Iran's cooperation with the IAEA has been “less than satisfactory” in “a number of respects.”[7] The report noted that Iran has failed to cooperate with the IAEA to resolve concerns about undeclared nuclear sites and material in Iran. The IAEA confirmed that Iran conducted undeclared nuclear activities at three locations—Lavisan-Shian, Varamin, and Turquzabad—until the early 2000s.[8] The IAEA published the comprehensive report on May 31 in response to an IAEA censure resolution in November 2024. The censure resolution was proposed by the E3 (the United Kingdom, France, and Germany).[9] The IAEA’s quarterly and comprehensive reports both confirm Iranian non-compliance with the Joint Comprehensive Plan of Action (JCPOA) and Non-Proliferation Treaty (NPT) Safeguards Agreement.
The United States and the E3 are planning to submit a resolution that formally declares Iran in non-compliance with its safeguards obligations in response to the recent IAEA reports, according to unspecified diplomats.[10] The United States and the E3 will reportedly submit the resolution at the next IAEA Board of Governors meeting on June 9 and 10. The resolution would lay the foundation for the E3 to trigger snapback sanctions. The JCPOA snapback mechanism allows JCPOA signatories to reimpose UN Security Council sanctions on Iran in the event of “significant non-performance by Iran of JCPOA commitments.”[11] The IAEA Board of Governors previously passed a similar resolution declaring Iran in non-compliance with its safeguards obligations in September 2005.[12] The Board of Governors referred Iran's non-compliance to the UN Security Council in February 2006, which led to the imposition of sanctions on Iran.[13] An unspecified senior Iranian official told Reuters on May 30 that Iran would respond to a resolution by “expand[ing] nuclear work.”[14]
Iran is likely trying to prevent a possible non-compliance resolution and snapback sanctions ahead of the June 9 IAEA Board of Governors meeting. Iranian Foreign Affairs Minister Abbas Araghchi held a phone call with IAEA Director General Rafael Grossi on June 1, during which Araghchi asked Grossi to explain “Iran's cooperation with the [IAEA]” at the Board of Governors meeting and warned that Iran would respond to “any inappropriate move by the European parties,” almost certainly referring to snapback sanctions.[15] Araghchi separately met with Grossi in Cairo, Egypt, on June 2.[16] Araghchi and Grossi’s meeting comes amid rising tensions between Iran and the E3. The E3 has threatened to trigger snapback sanctions on Iran if the United States and Iran do not reach a “substantial deal” by August 2025. An Iranian hardline outlet described a recent meeting between Iran and the E3 on May 16 as “tense.”[17] The same outlet claimed that the E3 demanded that any future agreement include a JCPOA-style snapback clause—a demand that Iranian officials have condemned as “illegal.”[18] Iranian officials have previously threatened a “serious response” if the E3 triggers snapback sanctions.[19] Iran could increase its near weapons-grade uranium stockpile or further expand its nuclear program in other ways in response to snapback sanctions.
The United States presented a written nuclear proposal to Iran via Oman on May 31.[20] Unspecified officials told the New York Times on May 31 that the proposal includes the establishment of a regional consortium comprised of Iran, the United States, Saudi Arabia, and other Arab states. Axios similarly reported on May 31 that the proposal includes the establishment of a regional consortium to enrich uranium for civilian purposes. Axios reported that the United States and IAEA would oversee the consortium and that the United States wants the consortium's enrichment facilities to be located outside of Iran, citing an unspecified source. The Iranian Foreign Affairs Ministry spokesperson emphasized on June 2 that a regional consortium “cannot in any way replace enrichment inside Iran.”
It is unclear if the United States would allow Iran to continue enriching uranium on Iranian soil if it agreed to join a regional consortium. The New York Times reported that the US nuclear proposal calls on Iran to completely cease uranium enrichment. Axios reported on June 2 that the proposal would allow “low-level uranium enrichment on Iranian soil” for an unspecified period of time.[21] Axios reported that Iran would reduce uranium enrichment to 3 percent, which is below the 3.67 percent limit in the JCPOA. The proposal also reportedly bars Iran from building new enrichment facilities conducting centrifuge research and development, and enriching uranium at underground facilities for an unspecified period of time. Under the proposal, Iran would limit enrichment activity at above-ground facilities and “dismantle critical infrastructure for conversion and processing of uranium.”
Iran is reportedly planning to reject the US nuclear proposal, which would likely further stall the US-Iran negotiations.[22] An unspecified Iranian diplomat close to the Iranian negotiating team told Reuters on June 2 that Iran is drafting a negative response to the proposal and considers the proposal a “non-starter” due to its failure to address Iranian interests or soften the United States’ stance on enrichment.[23] The source added that Iran's nuclear negotiations committee, which is under the supervision of Supreme Leader Ali Khamenei, assessed that the US proposal is “completely one-sided” and does not serve Iran's interests.[24] An Iranian expert close to the regime similarly stated on June 1 that the contents of the US nuclear proposal decrease the chances of Iran and the United States reaching a new deal.[25]
Israeli Prime Minister Benjamin Netanyahu's office called on the international community to “act now” against Iran following the release of the IAEA reports on May 31. Netanyahu's office described the reports as “a clear warning sign” that Iran is “totally determined to complete its nuclear weapons program.”[26] These statements come amid reports that Israel is preparing to strike Iranian nuclear facilities if the US-Iran nuclear negotiations collapse..[27] US President Donald Trump recently called on Netanyahu to avoid taking any action that could potentially jeopardize the US-Iran nuclear negotiations. [28]
The Iranian armed forces are continuing to prepare for potential US or Israeli strikes on Iran. The Financial Times reported on June 1 that Western intelligence and satellite imagery indicate that Iran has repositioned surface-to-air missile launchers, including S-300 air defense systems, near nuclear sites such as Natanz and Fordow.[29] Israeli airstrikes into Iran in April and October 2024 rendered Iran's four Russian-made S-300 air defense systems inoperable, and it is very unlikely that Russia has supplied Iran with new S-300 systems. The IDF rendered an Iranian S-300 inoperable in April 2024 by striking the S-300’s tomb stone engagement radar.[30] Iran displayed an S-300 with a “new, Iranian-designed” radar in February 2025.[31] The Artesh Air Defense Force conducted air defense exercises in northern and western Iran in January 2025, including near Fordow and the Arak heavy water reactor.[32]
Iranian commanders also continue to inspect air defense sites ahead of a potential Israeli or US strike on Iran. Artesh Air Force Commander Brigadier General Hamid Vahedi and his deputy, Brigadier General Ali Akbar Talebzadeh, inspected the 10th Tactical Air Base in Chabahar, Sistan and Baluchistan Province, on June 2.[33] Khatam ol Anbia Air Defense Headquarters Commander Brigadier General Alireza Sabahi Fard recently inspected Iran's Southeastern Air Defense Zone in Bandar Abbas, Hormozgan Province, on April 4 and May 30.[34] Artesh Commander Major General Abdol Rahim Mousavi conducted an inspection at the same air defense zone on May 16.[35]
https://www.understandingwar.org/backgrounder/iran-update-june-2-2025