The chief of the United Nations' nuclear watchdog met with top Iranian officials after Tehran pushed forward with a plan to begin using advanced centrifuges prohibited by the 2015 nuclear deal.
Iranian state television on September 8 broadcast video of Cornel Feruta, the acting head of the International Atomic Energy Agency, in Tehran.
He met with Foreign Minister Mohammad Javad Zarif and the head of Iran's Atomic Energy Organization, and emphasized the need for Iran's "full and timely cooperation" with UN nuclear agreements, according to an IAEA statement.
Feruta's visit came a day after Iran’s Atomic Energy Organization announced it would begin using two types of advanced centrifuges.
Iran already has crept past limits on nuclear enrichment and its uranium stockpile that were imposed by the 2015 deal.
Washington pulled out of the nuclear deal over a year ago, and has steadily ratcheted up economic and military pressure on Iran.
Tehran is also trying to pressure Europe to offer a way to sell crude oil abroad despite U.S. sanctions.
The UN nuclear agency said its inspectors were ready to check Iran's compliance.
"Agency inspectors are on the ground in Iran and they will report any relevant activities to IAEA headquarters in Vienna," spokesman Fredrik Dahl said.