US President Donald Trump and South Korea's Acting President Hwang Kyo-Ahn vowed Sunday to "strengthen" their joint defense capabilities against the belligerent North, the White House said.

"President Trump reiterated our ironclad commitment to defend the ROK, including through the provision of extended deterrence, using the full range of military capabilities," the White House said in a statement, using an acronym for the South's formal name.

"The two leaders agreed to take steps to strengthen joint defense capabilities to defend against the North Korean threat."