Iran Iran’s chief negotiator at this week’s talks aimed at curtailing Tehran’s nuclear program has charged the United States with involvement in a cyberattack on the country’s nuclear facilities.

Saeed Jalili told NBC News that Iran’s investigation has determined that the U.S. was involved in the attack using the Stuxnet computer worm, a virus which targeted centrifuges used to enrich uranium as part of Iran’s nuclear program. “I have witnessed some documents that show … their satisfaction in that [the U.S. was involved],” he said.