Iran retaliated to the re-imposition of sanctions lifted under the deal by breaching and going far beyond the nuclear restrictions. It is now enriching uranium to up to 60% purity, close to the 90% of weapons grade, and has enough uranium enriched to that level, if enriched further, for two atom bombs.

The head of the United Nations’ atomic watchdog has traveled to Iran where his agency faces increasing difficulty in monitoring the Islamic Republic’s rapidly advancing nuclear program.

Rafael Grossi, arrived in Tehran on Monday for the first talks with Iranian officials in more than a year. The visit comes at a turbulent time given the recent direct military clashes between Iran and Israel.

U.N. nuclear watchdog chief Rafael Grossi flew to Iran on Monday hoping to bolster his agency's oversight of Tehran's atomic activities after various setbacks, but analysts and diplomats say he has limited leverage and must be wary of empty promises.

In recent times, tensions have risen as Iran has faced fresh accusations of lack of cooperation on inspections of its nuclear facilities and other issues