South Korean President Yoon Suk-yeol reiterated that the U.S. and South Korea have upgraded their security partnership to a “nuclear-based alliance” in a Memorial Day speech on Tuesday, commemorating soldiers who helped to repel North Korean communists during the Korean War.

Yoon’s remark is his latest invocation of a phrase that Seoul officials have used several times since the U.S.-ROK summit in April, when Yoon and President Joe Biden agreed to establish a Nuclear Consultative Group (NCG) for joint planning on the use of U.S. nuclear assets.