Last week, Chinese and Russian officials joined Iranian President Mahmoud Ahmadinejad in a ceremony marking Iran's development of nuclear fuel plates used in a research reactor in Tehran.
Tehran said it secured the uranium from Turkey for use in a research reactor that produces radioisotopes for cancer treatment.
IAEA Deputy Director Herman Nackaerts was quoted by Iran's state-funded broadcaster Press TV as saying before his arrival in Tehran that he looked forward to a constructive visit.
"We hope to have a couple of good and constructive days in Tehran," he said.
The IAEA said last year there could be military dimensions to parts of Iran's nuclear program, which Tehran maintains is for peaceful purposes.
Washington had said it respects Iran's rights to peaceful nuclear research but worries Iran is working on the technology needed to develop a nuclear weapon.
Mark Hibbs, a nuclear proliferation expert at the Carnegie Endowment for International Peace, told The Guardian newspaper in London that the IAEA visit is a "make-or-break situation" for the Iranians.
"If (the IAEA) says Iran did not cooperate, Iran will be isolated in the boardroom," he said. "It will be much more difficult for Russia and China to veto further sanctions."
Iran announced it cut crude oil shipments to France and the United Kingdom in response to sanctions pressure.
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