"This has always been seen, for me at least, as a stopgap, as a measure to allow time for diplomacy," International Atomic Energy Agency (IAEA) Director General Rafael Grossi told reporters at Vienna airport after returning from talks in Iran.

Iran and the IAEA had earlier announced that they had agreed to allow inspectors to service the agency's surveillance equipment as Tehran has restricted access since earlier this year.

Grossi travelled to Iran Saturday for talks, days after the IAEA had criticised Tehran in a report for a lack of cooperation.

He said the agreement on servicing the agency's equipment would be put into practice "within a few days, very soon".

Grossi added that thanks to the agreement the agency will "be able to keep the information needed to maintain continuity of knowledge" of Iran's programme.

However, access to the information recorded by the equipment will have to wait for agreement at talks on reviving the 2015 nuclear deal, also known as the JCPOA.

"The reconstruction, the coming together of the jigsaw puzzle will come when there is an agreement at the JCPOA level," Grossi said.