Mohamed ElBaradei, director-general of the International Atomic Energy Agency, is due to visit within the next two days.
It will be his first trip to the country this year and comes amid growing pressure on Iran to suspend uranium enrichment activities.
A senior Iranian nuclear negotiator told the state news agency IRNA on the condition of anonymity: "The trip is within the framework of Iran's cooperation and consultation with the IAEA.
"ElBaradei will hold talks with a number of Iranian officials during his stay and Iran's outstanding issues with the IAEA will be discussed."
IAEA inspectors began their work by visiting the uranium enrichment facility in Natanz, after arriving in Tehran on Friday.
Enrichment is the process used to manufacture fuel for the civil nuclear power stations but can be also used to manufacture core material for atomic bombs.
The United Nations has called on Iran to suspend enrichment to provide a watertight guarantee that its nuclear programme is peaceful. Iran rejects charges that it is seeking atomic weapons.
Mohammad Saeedi of the Iranian Atomic Energy Organisation said: "Five inspectors, who arrived in Tehran on Friday, will begin their inspections on Saturday and will go to the enrichment facility in Natanz and the conversion facility in Isfahan."
However, Ali Asghar Soltaniyeh, Iran's representative to the IAEA, played down the importance of such inspections saying the visit was routine.
It was not related to a United Nations Security Council resolution which requires Iran to suspend its uranium enrichment related activities by the end of April 2006, he said.
Ali Asghar Soltaniyeh said the
inspections were not untoward
On Friday, a diplomat with the agency said ElBaradei would meet senior officials for discussions related to "outstanding safeguard verification issues and other confidence building measures requested by the IAEA board of governors".
"This visit will provide Iran an opportunity to come forward with information required by the IAEA to fill in the gaps in the history of Iran's nuclear activities,” he said.
"He's not going there to negotiate any settlement. His going there is part of an ongoing verification process and this requires face-to-face contact.
"He is going the extra mile to make the Iranians understand what is required for compliance. He will also remind them of the board's demands for confidence-building measures and why they are important."
Iran on January 10 resumed uranium enrichment research activities in Natanz however but added that it is ready to negotiate with the European countries the resumption of industrial enrichment.
ElBaradei has been in Iran twice before, in February and in October 2003.