North Korea vowed Wednesday to strengthen its nuclear weapons stockpile in order to deter a U.S. and South Korean military buildup in the region.

Speaking before the United Nations Wednesday, North Korea's Vice-Minister of Foreign Affairs Pak Kil Yon said Pyongyang is, however, ready to join nuclear nonproliferation efforts in its capacity as a nuclear weapon state.

"As long as the U.S. nuclear aircraft carriers sail around the seas of our country, our nuclear deterrent can never be abandoned but be should be strengthened further," Pak said. "This is the lesson we have drawn."

Pak defended Pyongyang's development of nuclear weapons, saying it has succeeded in preventing the Korean peninsula from being "turned into a war field scores of times."

He insisted that North Korea's stockpile of atomic weapons was exclusively for the purposes of self-defense and that his country hoped to abide by international treaties governing their use.

"As a responsible nuclear weapon state, we are willing to join in the international efforts for nuclear non-proliferation and safe management of nuclear material on an equal footing with other nuclear weapon states," he said.

North Korea's nuclear program is of intense concern because of worries the country is building its arsenal of atomic weapons. Pyongyang conducted two nuclear weapons tests in 2006 and 2009, drawing international condemnation and U.N. sanctions.

The U.S. is trying to restart stalled negotiations on North Korea's nuclear disarmament. North Korea walked out of the six-party talks last year amid international criticism of its long-range rocket launch. Prospects for resuming the talks dimmed after Pyongyang was accused of sinking of a South Korean warship in March.

Pak didn't say if his country was ready to return to talks but said a nuclear-weapon-free Korean peninsula would be achieved only if external nuclear threats are eliminated, a referrence to the U.S. presence in South Korea.

Pak denounced the U.S. as "disruptor of peace" in the Korean peninsula, saying ongoing U.S.-South Korean military exercises close to its border were provocative and causing tension.

North Korea has strongly objected to the drills, which came in response to the warship's sinking, claiming they are in preparation for an invasion.

Pak denied his country had anything to do with ship's sinking and questioned the credibility an investigation into the incident that found North Korea responsible.