Seoul - North Korea's military put its "strategic" rocket units on a war footing on Tuesday, with a fresh threat to strike targets on the US mainland, Hawaii and Guam, as well as South Korea.
"All artillery troops including strategic rocket units and long-range artillery units are to be placed under class-A combat readiness," the Korean People's Army supreme command said in a statement.
The units should be prepared to attack "all US military bases in the Asia-Pacific region, including the US mainland, Hawaii and Guam" and South Korea, said the statement carried by the Korean Central News Agency.
Despite a 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 mainland 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.
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.
Military tensions on the Korean peninsula have been at an elevated level for months, following December's rocket test and the North's third nuclear test which it carried out last month.
Both events triggered UN sanctions that infuriated the North, which has spent the past month issuing increasingly threatening statements about unleashing an "all-out war" backed by nuclear weapons.
Some have included similar warnings of looming strikes on US bases in the Pacific region, including Guam.
North Korea was particularly incensed that nuclear-capable US B-52 bombers flying out of Andersen Air base on Guam took part in recent joint South Korea-US military exercises.
"We will demonstrate the firm resolution of our people and military to protect our sovereignty and dignity through real military action," Tuesday's statement warned.
"There is no greater delusion than the idea that they will have an opportunity for retaliation," it added.
The statement coincided with the third anniversary of the sinking of a South Korean naval vessel by what Seoul insists was a North Korean submarine. Pyongyang has always denied any involvement.
Addressing a memorial ceremony for the 46 sailors who died in the incident, South Korean President Park Geun-Hye warned North Korea that its only "path to survival" lay in abandoning its nuclear and missile programmes.
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.