President Joe Biden and South Korea’s Yoon Suk Yeol unveiled a new plan on Wednesday to counter North Korea’s nuclear threat, with the US leader issuing a blunt warning that such an attack would “result in the end of whatever regime” took such action.

The new nuclear deterrence effort calls for periodically docking US nuclear-armed submarines in South Korea for the first time in decades, bolstering training between the two countries, and more. The declaration was unveiled as Biden hosted Yoon for a state visit at a moment of heightened anxiety over an increased pace of ballistic missile tests by North Korea.