Security Council, Iran will stop its voluntary measures, such as snap inspections, increased inspections of its nuclear sites, and also it will restart a uranium enrichment at a high industrial scale.

NPR: Reaction in Iran to Possible U.N. Sanctions

Without going into entirely boring detail, the Iranian plan for uranium enrichment depended on a series of high speed centrifuges.

FORBES: Stuxnet Was a Joint US/ Israeli Project

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