Rafael Grossi, the International Atomic Energy Agency's Director General, arrived in Tehran on Friday for discussions with officials, Iran's official Irna news agency reported.
A confidential IAEA report seen on Tuesday by AFP said uranium particles enriched up to 83.7 per cent — just under the 90 per cent needed to produce an atom bomb — had been detected at Iran's underground Fordo plant about 100km south of the capital.
The head of Iran's atomic energy organisation, Mohammad Eslami, said on Wednesday that Iran's production is at 60 per cent, according to state media.
Mr Grossi was met at the airport by Mr Eslami's deputy and his spokesman Behrouz Kamalvandi.
Tehran denies wanting to acquire atomic weapons, and last week said it had not made any attempt to enrich uranium beyond 60 per cent purity, adding that “unintended fluctuations … may have occurred” during the enrichment process.
The IAEA said last month that Iran substantially modified an interconnection between two centrifuge clusters enriching uranium, without declaring it to the agency.
A diplomatic source told AFP that Mr Grossi would also meet Iran's President Ebrahim Raisi to “relaunch the dialogue” on Iran's atomic work and to “reset the relationship at the highest level”.
During the visit, the IAEA chief will try to find out more and obtain “strengthened access to the [Fordo] site and an increase in the number of inspections”, the source said.
France, a signatory to a 2015 deal that promised Iran relief from biting economic sanctions in exchange for curbs on its nuclear activities, on Thursday described the new enrichment development as “unprecedented and extremely serious”.
