Speaking to the General Assembly, Ri Yong-ho said his country will "continue to take measures to strengthen its national nuclear armed forces in both quantity and quality."
He spoke just two weeks after North Korea's fifth and most powerful nuclear test provoked worldwide condemnation, prompting the UN Security Council to begin work on a new sanctions resolution.
"Going nuclear armed is the policy of our state," Ri, who has been foreign minister since May, told the world gathering.
"As long as there exists a nuclear weapon state in hostile relations with the DPRK (North Korea), our national security and the peace on the Korean peninsula can be defended only with reliable nuclear deterrence," he said.
North Korea has conducted two nuclear tests and test-fired more than 20 missiles this year alone.
After the latest blast on September 9, Pyongyang claimed it had significantly advanced its ability and tested a miniaturized nuclear bomb for a warhead that could be mounted on a missile.
In his address, Ri acknowledged that the nuclear tests "may not be easily understood by European countries," which he said were now "less sensitive" to security concerns decades after the end of the Cold War.
But the foreign minister described the nuclear explosions as "practical countermeasures" against the United States and a demonstration of the "strongest-ever will" of North Korea's ruling party and people.
Japan, South Korea raise alarm
Japan and South Korea used their addresses at the General Assembly this week to raise alarm bells over the threat from North Korea.
Japanese Prime Minister Shinzo Abe demanded that the world find a new way to confront Pyongyang after a decade of UN sanctions failed to change its behavior.
"The threat to the international community has become increasingly grave and all the more realistic," he said Wednesday. "It demands a new means of addressing it, altogether different from what we applied until yesterday."
South Korea's Foreign Minister Yung Byung-se suggested that the North could be stripped of its status as a member of the United Nations for refusing to accept the Security Council's decisions.
"I believe it is high time to seriously reconsider whether North Korea is qualified as a peace-loving UN member," he said in his address on Thursday.
However, such a proposal is likely to be opposed by China, Pyongyang's ally, which has repeatedly called for a de-escalation of tensions.
North Korea's membership in the United Nations -- the only major international forum where Pyongyang has a voice -- dates back 35 years to when the two Koreas were admitted simultaneously.
China, which is in negotiations with the United States on a new sanctions resolution, is also pushing for a resumption of six-party talks on North Korea's nuclear program.
Yung accused North Korea's government of engaging in a "fanatical and reckless pursuit" of nuclear and missile programs that had reduced the country to a wasteland of poverty and oppression.
Also voicing alarm, the North Korean foreign minister declared that the Korean peninsula had "turned into the world's hot spot" that could see "the outbreak of nuclear war."
But blame for the "root cause" of the crisis lies with the United States, he added, railing again against US-South Korea military exercises held twice this year.
