North Korean leader Kim Jong Un has said an elevated U.S. security partnership with South Korea and Japan poses a grave threat to his country and vowed to further bolster his nuclear weapons program.

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The first tour is set to take place Feb. 12 to 18, when major celebrations are planned for the birthday of the country's late leader Kim Jong Il, one of North Korea's biggest holidays.

North Korea said on Saturday its nuclear weapons are not meant for negotiations but are intended for combat use against enemies that threaten its people and world peace, its state media reported.

Kim Jong Un reiterated North Korea’s policy of developing its nuclear forces, saying he would bolster deterrence, as the nation marked the anniversary of the Korean People’s Army.

Leader Kim Jong Un pledged to pursue "sustained countermeasures," citing security ties between the U.S. and its regional allies.

North Korean leader Kim Jong Un has vowed to bolster his nuclear weapons program in response to the U.S.’s enhanced security partnership with South Korea and Japan. Last year, the U.S. expanded bilateral military exercises with South Korean and trilateral training with South Korea and Japan.

North Korea on Tuesday denounced the recent arrival of a U.S. nuclear-powered submarine in South Korea, accusing Washington of ignoring Pyongyang's security concerns and warning that it is ready to use any means to defend its national security.

North Korean leader Kim Jong Un has pledged to further develop the country's nuclear arsenal, citing increasing security threats from the United States, South Korea, and Japan. In a speech marking the 77th anniversary of the Korean People's Army,