These have included attacking centrifuges at Natanz with the Stuxnet computer worm in 2009, sabotaging imported equipment and disrupting supplies of key materials for manufacturing Iran's IR-1 centrifuges.

ECONOMIST: Iran and nuclear weapons

Amano noted that Iran has recently begun installing IR-2m centrifuges at its fuel enrichment plant at Natanz, and that those high-speed devices that rotate to enrich uranium are more advanced than the previously-installed centrifuges.

CNN: Nuclear watchdog agency says Iran not cooperating