The head of the United Nations nuclear watchdog, Mohamed ElBaradei, will go Tehran next week to discuss Iran's nuclear programme.
Mr ElBaradei will be holding discussions in Tehran
Mr ElBaradei will report back to the UN Security Council at the end of April on whether Iran has complied with its demand to suspend uranium enrichment.
The demand, issued last week, has been publicly rejected by Tehran.
UN nuclear inspectors arrived in Iran on Friday to visit sites including the Natanz uranium enrichment plant.
Iran insists it has the right to civilian nuclear technology and denies Western claims that it is seeking atomic weapons.
A senior official at the watchdog, the IAEA, said Mr ElBaradei would meet senior Iranian officials for talks on confidence-building measures.
The official said the visit would provide Iran with an opportunity to come forward with information required by the IAEA "to fill in the gaps in the history of Iran's nuclear activities".
Iran resumed small-scale uranium enrichment in January, citing research purposes.
It then scrapped snap inspections of its nuclear sites in February after the issue was referred to the UN Security Council. However, it has said it is continuing to co-operate with the IAEA.
The non-binding Security Council statement on Iran was approved on 29 March and gave Tehran 30 days to suspend uranium enrichment or face isolation.