North Korea also criticized U.S.-South Korean military exercises scheduled to begin Tuesday, saying they were a preparation for war. The North routinely makes such accusations whenever military drills are held in the South, but the rhetoric has been more bellicose recently because of tension over the North's nuclear development.
South Korea and its chief ally plan to hold an annual, training exercise called FOAL EAGLE for a month. The United States keeps 37,000 soldiers in the South, a legacy of the 1950-53 Korean War.
Washington says the nuclear issue is not bilateral and involves all countries concerned about nuclear proliferation. The U.N. Security Council is expected to debate the issue, and could impose sanctions — a move North Korea has threatened to treat as an act of war.
North Korea's official Korean Central News Agency accused the United States and Japan, which is within range of North Korean missiles, of using the alleged threat from North Korea as a pretext to plot war against the communist country.
The U.S.-Japanese strategy comes "at a time when the DPRK-U.S. confrontation is getting extremely acute and a touch-and-go military situation is prevailing on the Korean Peninsula," KCNA said. DPRK stands for Democratic People's Republic of Korea.
North Korea said its missiles "can never be a threat to other countries," and that Washington and Tokyo were using the North's missile program as an excuse to plan missile defense systems.
"The DPRK's production and deployment of missiles are a matter pertaining to its sovereignty in every respect and they are intended to increase its self-defensive military capability," KCNA said.
Missile exports are a major source of hard currency for impoverished North Korea.
U.S. officials have said they have no plans to invade North Korea, but are growing increasingly concerned about the North's reactivation of a nuclear reactor that is part of a suspected weapons program. Washington believes Pyongyang already has one or two nuclear weapons.
North Korea launched an anti-ship missile into the sea off its east coast on the eve of the inauguration of South Korean President Roh Moo-hyun on Feb. 24.
U.S. and South Korean officials played down the launch, saying the missile was small and conventional. However, there are fears that North Korea could test the long-range Taepodong-2 rocket, a more advanced rocket than the one it fired over Japan and into the Pacific in 1998.
U.S. defense experts believe that the missile, if deployed, could deliver a payload of several hundred pounds as far as Alaska or Hawaii, and a lighter payload to the western half of the continental United States.
In Seoul, a South Korean Unification Ministry official said on condition of anonymity that the international construction of two light-water nuclear reactors in North Korea had slowed because of the nuclear standoff with the North.
It was the first South Korean acknowledgment since the nuclear dispute began in October that construction of the reactors was in jeopardy.
The official was referring to a 1994 agreement under which a U.S.-led consortium was to build the power-generating reactors in exchange for the freezing of North Korea's nuclear facilities.
The deal unraveled late last year when U.S. officials said the North acknowledged it had a secret nuclear weapons program in violation of the 1994 deal. Washington and its allies suspended oil shipments, which were part of the agreement, and North Korea responded by moving to reactivate its frozen facilities.
The North contended that the slow construction of the reactors already nullified the deal. North Korea justifies its stance by claiming that it has a right to feel threatened by the United States, since the Bush administration considers it part of an "axis of evil," and has articulated a doctrine of preemptive use of force.
The administration has come under criticism for doggedly insisting on international support to prevent North Korea from expanding its arsenal, and avoiding even hints of a threat to use military force, while threatening to go to war against Iraq without U.N. authority.
"We would rather see North Korea not have any nuclear weapons," Secretary of State Colin Powell said last week, acknowledging that the U.S. believes North Korea may already have one or two.