Kim Jong-un calls for 'rapid expansion' of North Korea's nuclear capabilities

North Korean leader Kim Jong-un ordered the "rapid expansion" of North Korea's nuclear arsenal Tuesday, asserting that joint U.S.-South Korean military exercises could "ignite a war."

"The U.S.-ROK intensified military nexus and the muscle-flexing are the most obvious manifestation of their will to ignite a war," Kim said in remarks quoted by the official North Korean news agency and reported by AFP. "The prevailing situation requires us to make a radical and swift change in the existing military theory and practice and rapid expansion of nuclearization," he added.

The comments were made as Kim was visiting destroyer Choe Hyon on Monday. He then received a report on the ship's weapons system, on which he expressed satisfaction that "major tasks for making the navy high-tech and nuclear-armed" were "progressing as planned" ahead of an assessment in October, according to KCNA.

The United States and South Korea on Monday began joint military exercises in preparation for possible threats from North Korea. The 11-day series of drills includes "several large-scale, live-fire training events," the U.S. military said in a statement.

South Korean President Lee Jae Myung vowed Friday to "respect" the North Korean political system and build "military trust," a day after Pyongyang said it has no interest in improving relations with Seoul.