Rafael Grossi visited Tehran in late August to meet with Iranian officials to end a months-long impasse over the two locations thought to be from the early 2000s, AP reported.
During the visit, Iran agreed to allow the IAEA to inspect the two sites where the agency claimed Iran had stored or used undeclared nuclear material.
“I welcome the agreement between the agency and Iran, which I hope will reinforce cooperation and enhance mutual trust,” Grossi told the agency’s Board of Governors in Vienna.
He said that inspectors had already visited one site and would visit another later this month.
The IAEA chief added that the agency continues to verify the non-diversion of nuclear material declared by Iran under its Safeguards Agreement. “Evaluations regarding the absence of undeclared nuclear material and activities for Iran continue,” he told the 35-nation board.
Iran had been permitting IAEA inspectors in to current nuclear sites agreed upon in the landmark 2015 nuclear deal with world powers, but had said the other two sites dated from before the deal so there was no reason to grant access.
The country has also argued that the IAEA's access requests were based on allegations from Iran's archenemy Israel and have no legal basis.
The deal has been on life support since US President Donald Trump pulled his country unilaterally out of it in 2018 and reimposed sanctions on Iran.
In retaliation, a year after the US withdrawal, Iran rolled back part of its commitments to the deal that was meant to give it relief from sanctions in exchange for curbs on its nuclear program.