BERLIN (AP) — The head of the United Nations' atomic watchdog agency told board members on Monday he is hopeful Iran's decision to let inspectors in to two disputed sites could lead to greater trust with Tehran.

Rafael Grossi, director general of the International Atomic Energy Agency, in late August secured an agreement with Iran to inspect the two sites where the country is suspected of having stored or used undeclared nuclear material and possibly having conducted nuclear-related activities.

The agreement, which came after Grossi personally visited Tehran to meet with Iranian leaders, ended a months-long impasse over two locations thought to be from the early 2000s.

Iran had been permitting IAEA inspectors in to current nuclear sites agreed upon in the landmark 2015 nuclear deal with world powers, but had argued the other two sites dated from before the deal so there was no reason to grant access.

The IAEA in March identified the two sites as places where Iran possibly stored and/or used undeclared nuclear material or undertook nuclear-related activities without declaring them to international observers.

Grossi told the agency’s board of governors in Vienna that inspectors had already visited one site and would visit another later this month.

“I welcome the agreement between the agency and Iran, which I hope will reinforce cooperation and enhance mutual trust,” he said, according to a copy of his prepared remarks.

The ultimate goal of the nuclear deal is to prevent Iran from developing a nuclear bomb, which Iran insists it does not want to do.

Since President Donald Trump pulled the U.S. unilaterally out of the pact in 2018, Iran has steadily been violating restrictions on the amount of uranium it can enrich and the purity it is allowed to enrich to, and other limits.

But one reason the other countries involved — Germany, France, Britain, China and Russia — say that it's important to maintain the agreement is for the access IAEA inspectors continue to get to Iran's nuclear facilities.