The U.N. atomic watchdog on Friday flagged a new breach by Iran of its nuclear deal with major powers on the day those powers met to revive the agreement , a report by the agency seen by Reuters showed, likely raising tensions with Western powers.

The International Atomic Energy Agency avoids saying Iran has breached the deal. At the same time, it generally only issues such ad hoc reports to member states in the event of a breach. Two diplomats told Reuters what the report described amounted to a fresh breach.

The breach has to do with what counts officially toward Iran's stockpile of enriched uranium, a highly sensitive issue since that stockpile could be enriched further to weapons-grade material suitable for nuclear bombs if Iran chose to do so. It denies seeking such weapons and says its aims are entirely peaceful.