North Korea's Jan. 6 nuclear test did not expand its technical capability, but the U.S. government is keeping a close eye on Pyongyang's efforts to develop a thermonuclear warhead capable of reaching the United States, the head of the U.S. Missile Defense Agency said Tuesday.
"I would assess that their technical capability has not increased," Vice Admiral James Syring told an event hosted by the Center for Strategic and International Studies. "That said, everything that they're doing continues to be alarming and provoking. ... We continue to watch it closely."
Syring gave no further details on what was North Korea's fourth nuclear test.