The chief inspector of the United Nations nuclear watchdog has resigned from the agency that conducts inspections in Iran to verify compliance with the 2015 nuclear deal.
The Vienna-based International Atomic Energy Agency (IAEA) made the announcement on May 11, but gave no reason for Tero Varjoranta's unexpected departure.
The move comes days after U.S. President Donald Trump pulled out of the deal between Iran and world powers that provided Tehran with relief from sanctions in return for curbs on its nuclear program.
It is not known whether the U.S. move played any role in Varjoranta’s decision.
Varjoranta, a Finn, had since 2013 been a deputy director-general of the IAEA and head of its Department of Safeguards, which verifies countries' compliance with the nuclear non-proliferation treaty.
The IAEA said he will be replaced in an acting capacity by Massimo Aparo, head of the department's Iran team.
Trump on May 8 pulled the United States out of the nuclear deal, signed under his predecessor, Barack Obama.
The president has called the accord a “terrible” deal for the United States and accused Tehran of violating the "spirit" of the pact by continuing to test ballistic missiles and by supporting militant activity in the region.
Tehran has said its nuclear program is strictly for civilian use and denies supporting extremists in the Middle East.
Co-signees Britain, France, Germany, Russia, and China had urged Washington to remain a part of the deal, saying it was the best way to prevent Iran from acquiring nuclear weapons.
The IAEA has also repeatedly defended the agreement, saying it is a step forward in the global system of nuclear verification.