HYONHEE SHIN SOUTH Korea, the United States and Japan staged joint naval missile defence exercises to improve responses to North Korean threats, as Pyongyang accused Washington of ramping up "nuclear blackmail" with military drills. The three nations agreed at talks in Washington on Friday to hold regular missile defence and anti-submarine exercises in their efforts to boost diplomatic and military cooperation. North Korea tested a new solid-fuel intercontinental ballistic missile (ICBM) on Friday that experts say would ease the way for missile launches with little warning, part of an increase in its military activities in recent weeks. Hours after the trilateral exercises, Ri Pyong Chol, vice…