TALKS between Iran and the United States over Tehran’s nuclear programme are “in a very crucial” stage, the head of the United Nations nuclear watchdog said on Thursday.

The comments by Rafael Mariano Grossi, of the International Atomic Energy Agency, while on a visit to Tehran included an acknowledgement that his agency likely would be key in verifying Iranian compliance should a deal be reached. 

The two sides will meet again in Rome on Saturday for a new round of talks, after last weekend’s first meeting in Oman.