The International Atomic Energy Agency and Iran agree to adopt a "practical and pragmatic approach" to resolve issues, the UN agency's chief said on Saturday in Tehran.

The IAEA and Iran had "a lot of serious difficulties that we needed to handle," according to Rafael Grossi, but we have now "agreed to try a constructive, pragmatic way" to overcome them.

He made the remarks during a joint press conference with Mohammed Eslami, Head of the Atomic Energy Organization of Iran (AEOI), following talks viewed as critical to renewing the 2015 Iran nuclear deal.

Eslami said the two sides had come to the "conclusion that some documents which need to be exchanged between the IAEA and the Iranian organization should be exchanged" by May 22.

He added that "we have a program to enhance our nuclear activities within a peaceful framework." 

Ongoing talks in the Austrian capital to restore the agreement involve Iran, as well as Britain, China, France, Germany, and Russia directly, and the United States indirectly.

The talks began earlier today to hold detailed discussions in an effort to revive the nuclear agreement.

The AEOI announced on Friday night that Grossi had arrived in Tehran, where he was received by Behrouz Kamalvandi and other senior officials.

Grossi is scheduled to meet the head of the Iranian organization, Mohammad Eslami, and may also meet with Foreign Minister Hossein Amir-Abdollahian.