The International Atomic Energy Agency (IAEA) has been in talks with Tehran on how to fully restart its inspections of key nuclear sites after Tehran suspended cooperation with the agency following attacks by Israel and the United States in June.

The inspectors left Iran after Israel launched its unprecedented attack on June 13, striking nuclear and military facilities, with Washington later joining in with strikes on key nuclear facilities at Fordo, Isfahan and Natanz.

In late August, an IAEA team briefly returned to Iran to oversee the replacement of fuel at the Bushehr nuclear power plant.

Addressing a quarterly board meeting, IAEA chief Rafael Grossi said in a statement that "progress has been made" in talks on clinching a deal on the full resumption of inspections.

"It is my sincere hope that within the next few days it will be possible to come to a successful conclusion of these discussions in order to facilitate the resumption of our indispensable work with Iran," he said.

While details of the deal's "modalities" were still being hashed out, Grossi said that time was running out.

"There is still time, not much, but always enough when there is good faith and a clear sense of responsibility," he said on the opening day of the IAEA's 35-nation Board of Governors meeting.