North Korea's nuclear push is a 'serious concern': U.S. official

TOKYO -- North Korea's recent escalation of tensions such as missile launches and a potential nuclear test are "serious concerns," a high-ranking U.S. defense official said on Saturday.

Ely Ratner, assistant secretary of defense for Indo-Pacific Security Affairs, reaffirmed Washington's commitment to the complete denuclearization of the Korean Peninsula in a virtual speech at the Mount Fuji Dialogue in Tokyo.