Diplomats in Vienna, where the IAEA is based, said the visit was a fresh effort to get Iranian clarification about intelligence reports suggesting it is illicitly trying to design atomic bombs. Iran insists its nuclear work is peaceful.
"The two parties will assess the trend of cooperation between Iran's Atomic Energy Organization and the IAEA," IRNA said in a report that said Olli Heinonen, the IAEA's deputy director, would hold talks in Tehran on Thursday and Friday.
Western capitals have said Iran now faces a new round of U.N. sanctions after it failed to respond positively to an offer made by six world powers aimed at ending the dispute.
The powers proposed that Iran freeze any expansion of its nuclear work in return for a halt to further U.N. sanctions. Three other rounds of penalties have been imposed since 2006.
The freeze idea was aimed at getting preliminary talks going as a stepping stone towards formal negotiations on a package of nuclear, trade and other incentives. However, Iran would have to suspend uranium enrichment for those full talks to start.
Iran has refused to halt enrichment, which it says is aimed only at generating electricity. It has also given no indication that it is ready for a freeze. It has promised to give a "clear response" to the sextet's offer at an unspecified date.
Diplomats in Vienna played down speculation that Heinonen, was on a special mission to verify the current level of Iranian enrichment activity, noting Iran had given no apparent sign of openness to the powers' "freeze for freeze" proposal.
Enrichment is the part of Iran's work that most worries the West because it can be used to make fuel for power plants or, if desired, material for nuclear warheads.
(Reporting by Hashem Kalantari in Tehran and Mark Heinrich in Vienna, writing by Edmund Blair; Editing by Richard Balmforth)
