As Iran threatens to restart its nuclear program, the U.N.’s top nuclear inspector is calling it quits.

The International Atomic Energy Agency didn’t give a reason for Tero Varjoranta’s exit. It said on Saturday it doesn’t comment on personnel matters.

The departure came days after President Trump announced that the U.S. would withdraw from the 2015 deal with Iran over its nuclear program – prompting Tehran to say it is ready to reactivate that program on an “industrial scale.”

The Vienna-based IAEA has found no sign that Iran has breached the deal, known officially as the Joint Comprehensive Plan of Action.

Varjoranta, who is Finnish, was chief inspector since late 2013. He was responsible for policing the deal in Iran, and was highly regarded.

He was replaced on a temporary basis by Massimo Aparo, the acting director of the agency’s Office for Verification in Iran. Aparo, who is from Italy, is a nuclear engineer who has worked with the agency since 1997. A permanent replacement will be appointed as soon as possible, the IAEA said.

The 2015 deal between Tehran and major world powers forced Iran to open any site to the IAEA within 24 days. The agency has conducted hundreds of inspections inside Iran since the deal was signed, and issued regular reports confirming that the country is complying.

The other nations involved in the deal, including Russia, China and European powers, say they want to keep it alive.

Despite the US’s withdrawal from the pact, American officials said that they want the IAEA’s inspections in Iran to continue.

“The United States will continue to support robust implementation of IAEA inspections in Iran to the full extent of the IAEA’s authority,” an official at the US mission to the IAEA told AFP.

With Post Wire Services