North Korea has warned that the United States will pay dearly if it re-lists Pyongyang as a state sponsor of terrorism following the alleged murder of leader Kim Jong-Un's half-brother in Malaysia last month. Kim Jong-Nam was killed on 13th of this month at a crowded Kuala Lumpur airport in an attack with VX toxic nerve agent, which is considered a weapon of mass destruction.<br/><br/>Seoul has said from the start that North Korea is behind the Cold War-style assassination. South Korean and Japanese media, citing diplomatic sources, have since reported that the US has been mulling placing the North back on its terror list, which includes Iran and Syria.