Vienna International Centre, where IAEA offices are located
Vienna International Centre, where IAEA offices are located iStock

The International Atomic Energy Agency (IAEA), the UN’s atomic watchdog, said Thursday it believes that Iran has further increased its stockpile of highly enriched uranium and criticized Tehran for continuing to bar the agency's officials from accessing or monitoring Iranian nuclear sites, The Associated Press reported.

In its quarterly report, the IAEA said that according to its assessment, as of Oct. 22, Iran has an estimated 62.3 kilograms of uranium enriched to up to 60% fissile purity. That amounts to an increase of 6.7 kilograms since the IAEA's last report in September.

That enrichment to 60% purity is one short, technical step away from weapons-grade levels of 90%. Nonproliferation experts have warned in recent months that Iran now has enough 60%-enriched uranium to reprocess into fuel for at least one nuclear bomb.

The IAEA report also estimated that as of Oct. 22, Iran’s stockpile of all enriched uranium was at 3673.7 kilograms — a decrease of 267.2 kilograms since the last quarterly report in September, according to AP.

The IAEA said it was unable to verify the exact size of Iran’s stockpile of enriched uranium due to limitations that Tehran imposed on UN inspectors last year and the removal of the agency’s monitoring and surveillance equipment in June at sites in Iran.

A separate report, also seen by the AP, said IAEA Director General Rafael Grossi is “seriously concerned” that Iran has still not engaged on the agency’s probe into man-made uranium particles found at three undeclared sites in the country. The issue has become a key sticking point in the talks on a revival of the 2015 Iran nuclear deal.

Those negotiations have been on hold for several weeks and do not appear to be on track to be revived anytime soon.

Iran in September announced it had submitted its comments to the US response to the European Union’s draft for reviving the 2015 Iran nuclear deal.

While Iran’s Foreign Ministry spokesperson said at the time that Iran’s response was prepared based on a constructive approach, a senior Biden administration official said the Iranian response "is not at all encouraging.”

A US official later said that the efforts to revive the 2015 Iran nuclear deal have “hit a wall” because of Iran's insistence on the closure of the UN nuclear watchdog's investigations.

The US Special Envoy for Iran, Rob Malley, said last week that the US is focused on matters on Iran “where we can be useful,” and is not currently going to “waste our time” on the nuclear deal “if nothing’s going to happen.”