The United Nations nuclear watchdog on Wednesday referred Iran to the U.N. Security Council for the first time in 20 years, escalating a long-running dispute over Tehran’s nuclear program and its refusal to provide inspectors access to key sites.

The International Atomic Energy Agency’s 35-member board of governors approved the resolution by a vote of 23-3, with eight abstentions and one country not voting. China, Russia, and Niger opposed the measure. The United States, the United Kingdom, France, and Germany put forth the resolution.