The United Nations’ atomic watchdog passed a resolution of censure against Iran on Wednesday, deepening a diplomatic rift over the Islamic Republic’s contested nuclear program.

European diplomats proposed the measure after International Atomic Energy Agency inspectors reported that Iran hasn’t helped them resolve a probe into uranium particles, presumed to be decades old and detected at undeclared locations.

Twenty mostly-Western countries voted for the censure. China and Russia opposed the motion with the rest of the IAEA’s 35-member board abstaining, according to diplomats at the meeting. The three-page censure, drafted by France, Germany and the U.K., said it was "essential and urgent” that Iran cooperates on the issue of the unexplained fissile matter.