North Korean state television broadcasts footage of Kim Jong Un attending an "urgent operation meeting" with senior generals late last month, during which he signed a rocket preparation plan and ordered his forces on standby to strike the US mainland, South Korea, Guam and Hawaii.
In the last few weeks, Kim has responded with fury over United Nations sanctions following North Korea's third nuclear test 12 February and over ongoing US-South Korean military exercises.
Among other statements, Pyongyang has threatened a nuclear strike against the US, declared that it has scrapped the Korean War armistice, blocked South Koreans from entering a jointly run industrial park and announced that it will restart a plutonium reactor and produce more fuel for nuclear bombs.
On Thursday, South Korea's defence minister reported that the North had moved a missile with "considerable range" to its east coast, but emphasised that the missile was not capable of reaching the United States and that there were no signs that the North was preparing for a full-scale conflict.
Analysts say Pyongyang's ominous warnings in recent weeks are probably efforts to provoke softer policies from South Korea, to win diplomatic talks with Washington and solidify the image of its young leader.
A former US foreign policy advisor on Friday said the sabre-rattling by Kim Jong Un showed he was trying to "create a power base".