Iran’s nuclear chief played down on Wednesday a finding from the International Atomic Energy Agency (IAEA) that it had detected uranium particles almost suitable for nuclear weapons in Iran.

“A slight fluctuation was detected in one of the tests, but it couldn’t even be seen with a microscope,” Iran’s nuclear chief Mohammad Eslami said in Tehran.

In a letter from February 20, Iran informed the agency that “unintended fluctuations in enrichment levels may have occurred” in November.

According to the IAEA, uranium had a purity level of 83.7% - just short of the 90% needed to build a nuclear weapon. Iran has been suspected of working on its own nuclear bomb for many years.

The traces were discovered back in January during an inspection of an Iranian facility at Fordo, where uranium is produced to a purity of 60%.

IAEA chief Rafael Grossi officially confirmed the find for the first time on Tuesday evening in Vienna. Talks are now underway with Tehran to clarify the matter, according to a non-public report obtained by dpa.

“You can do it by mistake or you can do it intentionally,” said a senior diplomat who closely follows Iran’s nuclear programme.

He added that similar changes have also occurred in enrichment plants in other countries.

But in Iran’s case, it was “quite a big jump” from 60% to almost 84%.

However, the analyses so far had shown that only a very small amount of 83.7% material had been produced, the diplomat said.

Grossi said in January that Iran already has enough enriched uranium for several nuclear weapons if the material were enriched to an even higher level.

However, Tehran still has a long and difficult road ahead of it before it can develop a nuclear weapon, Grossi said. Tehran always stresses that it is only interested in the peaceful use of nuclear technology.

According to the IAEA report, the Islamic Republic possesses nearly 435 kilogrammes of 20% uranium, 48 kilos more than in the previous quarterly report in November. The stock of 60% uranium increased by 25 kilos - currently just under 88 kilos.

Grossi has repeatedly pointed out that even 60% of uranium is almost weapons-grade.

In 2015, Iran pledged to limit its nuclear programme after the Joint Comprehensive Plan of Action, known as the JCPOA, was negotiated with former US president Barack Obama’s administration.

In return, Western sanctions were lifted. The JCPOA was intended to prevent the authoritarian-ruled country from joining the circle of nuclear powers.

Under Obama’s successor, former US president Donald Trump, the United States withdrew from the agreement in 2018. Tehran responded by expanding uranium enrichment and restricting IAEA inspections. Negotiations to revive the agreement are on hold.

Last year, the IAEA had to dismantle 27 surveillance cameras in Iran. Grossi, stressed however that in view of the latest find, his inspectors would continue to be able to detect important developments within a short time.