U.S. Deputy Secretary of Defense Ashton Carter listened to reporters' questions during a news conference at U.S. Embassy in Seoul, South Korea on Monday. Deputy Secretary of Defense Carter told reporters Monday that Pyongyang's threats would only deepen Washington's defense commitment to Seoul. He says that includes a "nuclear umbrella" security guarantee for Seoul, which doesn't have atomic weapons. He also notes flight training Tuesday of a B-52 bomber. The B-52 is nuclear capable.