The head of the United Nations atomic watchdog arrived in Tehran on Saturday to pave the way for a visit by UN inspectors to Iran's new uranium enrichment plant at the holy city of Qom, local media said.
Mohamed ElBaradei's visit comes after Washington and its allies demanded rapid progress in revived talks on Iran's controversial nuclear programme.
The International Atomic Energy Agency (IAEA) chief is expected to meet Ali Akbar Salehi, the head of the Iranian Atomic Energy Organisation, and other officials on Sunday, news agencies said.
The main purpose of his visit is to discuss with Iranian officials "how UN inspectors can visit the Qom plant, other nuclear facilities and to discuss more cooperation," the ILNA news agency said.
Fars news agency quoted Ali Shirzadian, spokesman for Iran's atomic body, as saying that ElBaradei will also discuss how fuel can be provided for Tehran's research reactor.
Shirzadian stressed said that ElBaradei's visit was planned prior to talks in Geneva last Thursday between six world powers and Tehran and has "no connection" with the high-profile negotiations.
Iran's English-language Press TV said ElBaradei would himself not visit the Qom facility during his trip.
It quoted the Iranian Atomic Energy Organisation as saying in a statement that the visit was also aimed at the "continuation of cooperation to supply fuel for Tehran research reactor."
The disclosure prior to the Geneva talks by Iran that it is building a nuclear enrichment plant inside a mountain at Qom had triggered worldwide outrage.
ElBaradei would leave the country late tomorrow or early Monday, an Iranian official familiar with his visit told AFP.
His visit comes amid mounting international pressure against Iran over its uranium enrichment programme, including a demand by US President Barack Obama after Thursday's talks in Geneva for swift and "constructive" action by Tehran.
Obama warned that his patience for dialogue was limited.
But he conceded that the Geneva meeting, which included the highest-level direct talks between the United States and Iran in three decades, marked a "constructive" start to defusing the nuclear standoff.
President Mahmoud Ahmadinejad today defended Tehran's nuclear programme, including the building of the Qom plant.
"Iran's actions are based on honesty. We did not have any secret (nuclear) work because we gave information (about the new plant) ahead of time" to the IAEA, Ahmadinejad said at a ceremony in Tehran.