North Korean leader Kim Jong Un 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, state media reported Sunday.

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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 Korean leader Kim Jong Un criticised trilateral military cooperation among the United States, Japan and South Korea for raising tensions in the region and vowed countermeasures, including the further development of nuclear forces.