An officer from the North Korean military vowed to exact \"merciless revenge\" on the South Korean president for what he said was slander against Pyongyang. North Korea this week demanded an apology from South Korean President Lee Myung-bak after South Korean media outlets described a six-day ceremony in Pyongyang as state propaganda. North Korea, in response, said it was entering the coordinates of South Korean media outlets into its military strike systems. North Korean military officer Han Chol Chu told the state-run Korean Central News Agency that he was seeking revenge against the \"rat\" Lee. \"I will take merciless revenge on not only the rat but also conservative media in South Korea hell-bent on making rubbish,\" he was quoted as saying. Washington this week sent its top North Korean policy officials to Europe and Asia to discuss the crisis in the Korean Peninsula. North Korea is believed to be preparing for a nuclear test following the failed April launch of a long-range rocket. Similar launches in 2006 and in 2009 coincided with test of North Korean nuclear devices.