The U.S. and South Korea held the first meeting of their new Nuclear Consultative Group (NCG) in Seoul on Tuesday, repeating their vow to “end” the North Korean regime if it uses weapons of mass destruction.

The meeting to discuss joint nuclear planning was timed with the allies’ announcement that the USS Kentucky, an American Ohio-class nuclear submarine, had arrived in the South Korean port of Busan — the first visit by a submarine capable of carrying nuclear-equipped ballistic missiles in around four decades, according to Seoul.