Foreign Minister Ri Yong-ho made the pledge during an address before the U.N. General Assembly, claiming that the Korean Peninsula has now been turned into "the world's most dangerous hotspot which can even ignite the outbreak of a nuclear war."
"The successful nuclear warhead explosion test that we have conducted recently is part of practical countermeasures to the rackets of threats and sanctions of the hostile forces, including the United States," Ri said.
"The DPRK will continue to take measures to strengthen its national nuclear armed forces in both quantity and quality in order to defend the dignity and the right to existence and safeguard the genuine peace vis-a-vis increased war threats of the U.S.," he said.
His speech was a focus of attention because it came just two weeks after the North stunned the world with its fifth nuclear test, the most powerful so far, showing the regime is making headway.
Ri said U.S. "hostile policy" motivated the North to develop nuclear bombs.
"The DPRK had no other choice but to go nuclear inevitably after it has done everything possible to defend the national security from the constant nuclear threats from the U.S.," he said. "Our decision to strengthen (our) nuclear armament is a righteous self-defensive measure to protect ourselves from constant nuclear threats of the United States."
Ri also said that nuclear armament is now the "policy of our state."
"As long as there exists a nuclear weapons state in hostile relations with the DPRK, our national security and the peace on the Korean Peninsula can be defended only with reliable nuclear deterrence," he said, referring to the U.S.
"Only a couple of days ago, the United States again threatened the DPRK by flying the B-1B strategic bomber over the military demarcation line on the Korean Peninsula and landing in South Korea," he said. "The United States will have to face tremendous consequences beyond imagination."
Ri reiterated the North's long-running claims that U.S.-South Korea joint military exercises are evidence of U.S. hostile policy. Pyongyang brands the annual exercises as a rehearsal for invasion despite repeated assurances from Washington and Seoul that they are purely defensive.
Ri said such drills are "extremely provocative," "thoroughly offensive," and "aggressive nuclear war exercises."
He also accused the U.N. Security Council of double-standards, saying the global security body takes issue only with the North's nuclear and missile tests while remaining silent about such weapons tests by other nations.
"The U.N. Security Council is a place where guilt is decided not on the basis of justice, but by the criterion whether one has veto power or not," he said. "The United States has no more qualification to force U.N. members to implement this kind of undeserved resolution while the member states have no more obligation to implement this unfair and unjust resolution." (Yonhap)