South Korea and the United States are moving to employ their latest detection equipment to prepare for North Korean chemical and biological weapons in the joint military drill planned for this year, sources said Sunday. The move is in response to Pyongyang being accused of using the lethal VX nerve agent to kill Kim Jong-nam, the estranged half brother of North Korean leader Kim Jong-un, at a crowded airport in Malaysia on Feb. 13. The allies have been conducting the Able Response chemical and biological warfare exercise every year for the past six years.