SEOUL: North Korean leader Kim Jong Un has vowed to accelerate Pyongyang's nuclear buildup and warned the United States against making a 'wrong decision' after overseeing the launch of his country's most powerful ballistic missile, state media said on Tuesday.

Monday's test launch of the solid-fuel Hwasong-18 came a day after the nuclear-powered submarine USS Missouri made port in the South Korean city of Busan and followed a US-South Korea warning that a nuclear attack by North Korea would mean 'the end of the Kim regime.'