North Korea's Foreign Minister Ri Su Yong addresses the Conference on Disarmament at the United Nations in Geneva March 3, 2015. North Korean Foreign Minister Ri warned on Tuesday that his country had the power to deter an "ever-increasing nuclear threat" by the United States with a pre-emptive strike if necessary. In a rare speech to the U.N.-backed Conference on Disarmament, Ri said joint military exercises being staged by South Korea and the United States were "unprecedentedly provocative in nature and have an especially high possibility of sparking off a war." REUTERS/Denis Balibouse (SWITZERLAND - Tags: POLITICS HEADSHOT)