North Korea has put its strategic rocket units on combat-ready status, with orders to prepare for possible strikes against the United States mainland and Hawaii.But many analysts doubt that Pyongyang even has the capability to hit the US.
The North Korean regime is enraged that the US has recently flown B-52 bombers over the Korean Peninsula, and has accused Washington of preparing an invasion.
In response, the North Korean army command has ordered all artillery troops and strategic rocket units to be ready for combat.
A statement from the Korean People's Army supreme command ordered rocket units to be prepared to attack "all US military bases in the Asia-Pacific region, including the US mainland, Hawaii and Guam".
Despite its successful long-range rocket launch in December, most experts believe North Korea is years from developing a genuine inter-continental ballistic missile that could strike the continental United States.
Hawaii and Guam would also be outside the range of its medium-range missiles, which would be capable, however, of striking US military bases in South Korea and Japan.
North Korean leader Kim Jong-Un has spent the past few weeks touring frontline military units, monitoring live fire artillery drills and making inflammatory speeches about wiping out the enemy.
Sabre-rattling and displays of brinkmanship are nothing new in the region, but there are concerns that the current situation is so volatile that one accidental step could escalate into serious conflict.
"We are closely monitoring the situation. So far there has been no particular North Korean troop movement," a South Korean defence ministry spokesman said.
North Korea's patron and sole major ally China was quick to urge calm from all sides.
"We hope that relevant parties will exercise restraint so as to ease the tension," foreign ministry spokesman Hong Lei said.
The supreme command announcement came days after the South Korean and US militaries signed a new pact, providing for a joint military response to even low-level provocative action by North Korea.
While existing agreements provide for US engagement in the event of a full-scale conflict, the new protocol addresses the response to a limited provocation such as an isolated incident of cross-border shelling.
It guarantees US support for any South Korean retaliation and allows Seoul to request any additional US military force it deems necessary.
North Korea shelled a South Korean border island in November 2010, killing four people.