Iran on Sunday demanded that the UN nuclear watchdog “completely” resolve outstanding issues related to questions over nuclear material at undeclared sites, amid resumed talks to revive its 2015 nuclear deal. Talks aimed at reviving the agreement over Iran’s nuclear programme resumed this week in Vienna, months after they had stalled. Iranian sources have suggested that one of the key sticking points is a probe by the International Atomic Energy Agency on traces of nuclear material found at undeclared Iranian sites. “We believe that the agency should completely resolve the remaining safeguard …