The head of the UN atomic watchdog was due to hold talks Sunday with senior Iranian officials on allowing its inspectors into 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 in Geneva last week on Iran's controversial nuclear programme. The International Atomic Energy Agency (IAEA) chief was 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.
Iran's English-language Press TV said ElBaradei would not visit the Qom facility himself during his trip.
The disclosure prior to the Geneva talks by Iran that it is building a second nuclear enrichment plant inside a mountain at Qom triggered worldwide outrage.
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 said 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.
But he warned that his patience for dialogue was limited, and made a thinly-veiled threat Washington would press for further UN sanctions if Tehran fails to take quick action.
Western powers suspect Tehran is making an atomic bomb under the guise of its civilian nuclear work, a charge Iran denies.
President Mahmoud Ahmadinejad on Saturday 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.
The Geneva talks were the first of their kind for 15 months, and Western officials acknowledged they marked Iran's "engagement" on its nuclear programme, which they said Iran had refused to discuss since July 2008.
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.
Iran also tentatively agreed at the Geneva talks to ship some of its stocks of low enriched uranium (LEU) abroad for processing into fuel for an internationally supervised research reactor in Tehran.
Amid fears among Western powers that Iran may have amassed enough low LEU to eventually create a nuclear bomb, senior US officials have said such a move might help lower tensions.
"If Iran agrees to send most of its stockpile of LEU to Russia to be further enriched to provide this fuel, it will reduce that source of anxiety," a US official who declined to be named told journalists.
However, the agreement is only "in principle" and the technical details need to be worked out at an IAEA meeting in Vienna on October 18.
ElBaradei was expected to leave the country late on Sunday or early Monday, an Iranian official familiar with his visit told AFP.