Iran has done little to answer the U.N. nuclear watchdog's long-standing questions on the origin of uranium particles found at three undeclared sites despite a fresh push for a breakthrough, the watchdog said in a report seen by Reuters on Monday.
The lack of progress could set up a new diplomatic clash with the West when the International Atomic Energy Agency's 35-nation Board of Governors meets next week. If Western powers seek a resolution criticising Tehran it could deal a further blow to stalled efforts to revive the 2015 nuclear deal.
The fresh quarterly IAEA report detailing Iran's continued failure to provide satisfactory answers raises pressure on the United States and its allies to take action against Iran at the board meeting, since Tehran and the IAEA announced a renewed push in March to clear things up by now.
"Iran has not provided explanations that are technically credible in relation to the Agency's findings at those locations," the report said, adding: "The safeguards issues related to these three locations remain outstanding."
A separate quarterly IAEA report seen by Reuters said Iran's stockpile of uranium enriched to 60% - close to the roughly 90% that is weapons grade, in the form that can be fed into uranium-enriching centrifuges - is estimated to have grown by 9.9 kg to 43.1 kg.
That amounts to more than what the IAEA calls a "significant quantity" defined as "the approximate amount of nuclear material for which the possibility of manufacturing a nuclear explosive device cannot be excluded" - or theoretically enough material, if enriched further, to make a nuclear bomb.
At 60% purity a significant quantity would be around 42 kg of uranium.
Western powers fear Iran is getting closer to being able to sprint towards producing a nuclear bomb if it chose to, though Iran says its intentions are entirely peaceful.
(Reporting by Francois Murphy; Editing by Gareth Jones)
