South Korean President Yoon Suk-yeol boarded a visiting U.S. nuclear missile-armed submarine Wednesday afternoon and warned the North Korean “regime would end” if they commit a “nuclear provocation,” according to the ROK Presidential Office.

Yoon boarded the USS Kentucky, an Ohio-class nuclear ballistic missile submarine (SSBN), with his wife Kim Keon-hee around 3 p.m. KST at the joint U.S.-ROK Busan Naval Base in the south of the country, after the allies announced the vessel’s arrival the previous day.