Iran officially suspended its cooperation with the U.N. nuclear watchdog on Wednesday, a move the United States described as "unacceptable."

It came after last month's 12-day conflict between Iran and Israel, which saw unprecedented Israeli and U.S. strikes on Iran's nuclear facilities and sharply escalated tensions between Tehran and the International Atomic Energy Agency (IAEA).

On June 25, a day after a ceasefire took hold, Iranian lawmakers voted overwhelmingly to suspend cooperation with the Vienna-based IAEA. State media confirmed on Wednesday that the legislation had now taken effect.