A number of new generation Iranian centrifuges are seen on display during Iran’s National Nuclear Energy Day in Tehran, Iran April 10, 2021. Iranian Presidency Office/WANA (West Asia News Agency)/Handout

Iran’s stock of uranium enriched to up to 60%, close to weapons-grade, has grown to well above the amount that by one definition is enough, if enriched further, for a nuclear bomb, a UN atomic watchdog report showed on Wednesday.

Iran‘s uranium enriched to up to 60% and in the form of uranium hexafluoride, the gas that centrifuges enrich, is estimated to have grown by 12.5 kg to 55.6 kg since the last quarterly International Atomic Energy Agency report issued on May 30, the IAEA report to member states seen by Reuters said.

At the same time, as in previous quarters, the IAEA issued a second report saying Iran had still not provided credible answers on the origin of uranium particles found at three undeclared sites that appear to mainly be old and which the IAEA has been investigating for years.

“The Director General is increasingly concerned that Iran has not engaged with the Agency on the outstanding safeguards issues during this reporting period and, therefore, that there has been no progress towards resolving them,” the second report, also seen by Reuters, said.

The issue of the undeclared particles has been a sticking point in negotiations to revive the 2015 Iran nuclear deal, with Iran seeking to have the investigation closed while Western powers and the IAEA insist it is a separate matter that Iran is legally obliged to help clear up as a signatory to the nuclear Non-Proliferation Treaty.

US intelligence agencies and the IAEA believe Iran had a secret, coordinated nuclear weapons program that it halted in 2003. Iran, however, insists it never had such a program. Most of the sites are thought to date back to around 2003 or earlier.

“The Agency is not in a position to provide assurance that Iran‘s nuclear program is exclusively peaceful,” the second report said, meaning that without credible explanations from Iran on what happened to the uranium that appears to have been present at the three sites, the agency could not guarantee that uranium had not been siphoned off to make weapons.