Gen. Pat Ryder told reporters Thursday that deterrence of North Korea "continues to work," hours after the Kim regime launched another intercontinental ballistic missile. North Korea claimed on Friday morning that it tested a "nuclear underwater attack drone" this week amid joint U.S. and South Korean military drills, according to state media outlet Korean Central News Agency. The new underwater weapon is designed to "stealthily infiltrate into operational waters" and target naval striker groups and enemy ports, North Korea claimed. "This nuclear underwater attack drone can be deployed at any coast and port or towed by a surface ship for operation," KCNA said in a statement. A test warhead exploded in the waters off Hongwon Bay on Thursday afternoon, North Korea claimed.