A Foreign Ministry spokesman said the North had built atomic weapons to counter the U.S. nuclear threat.
"As we declared, our strong revolutionary might put in place all measures to counter possible U.S. pre-emptive strike," the spokesman said, according to the Korean Central News Agency. "Pre-emptive strike is not the monopoly of the United States."
The United States urged North Korea to return to international nuclear negotiations instead of making inflammatory statements. State Department spokesman Sean McCormack said the United States has no plans to invade or attack North Korea.
Last week, the communist country warned that it had the right to launch a pre-emptive strike, saying it would strengthen its war footing before joint South Korea-U.S. military exercises scheduled for this weekend.
The North's spokesman said it would be a "wise" step for the United States to cooperate on nuclear issues with North Korea in the same way it does with India.
Earlier this month, President Bush signed an accord in India that would open some of its atomic reactors to international inspections in exchange for U.S. nuclear know-how and atomic fuel.
The accord was reached even though New Delhi has not signed the international Nuclear Nonproliferation Treaty. North Korea has withdrawn from the treaty and condemned the United States for giving India "preferential" treatment.
"If the U.S. is truly interested in finding a realistic way of resolving the Korean Peninsula nuclear issue, it would be wise for it to come out on the path of nuclear cooperation with us," the North Korean spokesman said.