North Korea has restarted production of plutonium fuel, a senior State Department official said on Tuesday, showing that it plans to pursue its nuclear weapons program in defiance of international sanctions. The U.S. assessment came a day after the U.N. nuclear watchdog said it had “indications” that Pyongyang has reactivated a plant to recover plutonium from spent reactor fuel at Yongbyon, its main nuclear complex.

The latest developments suggest North Korea’s reclusive communist government is working to ensure a steady supply of materials for its drive to build warheads, despite tightened international sanctions after its fourth nuclear test in January. FULL REPORT