Tehran vows to 'respond firmly and appropriately to any unconstructive action' taken by the IAEA, which says it still has questions regarding presence of nuclear material

UN watchdog report finds Iranians withholding answers to long-posed questions; Tehran says assessment influenced by 'Zionist regime and some other actors'

Move comes just weeks after Tehran said it set up another site for producing centrifuges in Isfahan, where UN watchdog doesn't have access to data collected by its cameras

US State Department says it is 'comparing notes' with Israel and Gulf allies ahead of the resumption of negotiations in Vienna later this month

Iranian atomic agency chief tells IAEA that Karaj site was 'severely damaged' in June attack that Tehran previously said it thwarted

Head of UN nuclear watchdog upbeat after reaching a deal in Tehran to renew inspectors' access to nuclear site surveillance equipment