BRUSSELS/PARIS (Reuters) -The head of the United Nations’ atomic watchdog said on Tuesday Iran was dragging its feet on information about uranium particles found at old undeclared sites in the country, raising the prospect of a clash on the issue in June. Talks to revive Iran’s 2015 nuclear deal with world powers have been on hold since March, chiefly over Tehran’s insistence that Washington remove the Islamic Revolutionary Guard Corps (IRGC), its elite security force, from the U.S. Foreign Terrorist Organization (FTO) list. While not technically part of the nuclear deal, one issue causing ten…