Scott A. Snyder, Senior Fellow for Korea Studies and Director of the Program on U.S.-Korea Policy
North Korea's capability to threaten the United States comes in two forms:
The possibility that North Korean-origin fissile material could be sent to the United States, either through sale to terrorist groups or by delivering a nuclear device to a U.S. harbor by boat, or;
The ability to threaten U.S. interests abroad, including through renewed conflict on the Korean peninsula, where twenty-eight thousand U.S. forces are stationed with the mission of defending South Korea from North Korean aggression.
North Korea does not yet have the capability to strike the United States with a nuclear-loaded intercontinental ballistic missile but it is attempting to perfect that technology. Reports in late 2013 suggested that North Korea might attain such a capability by 2015; former U.S. secretary of defense Robert Gates stated in early 2011 that North Korea might have that capability within five years. North Korea's December 2012 satellite test using ballistic missile technology succeeded in launching an object into orbit around the earth, but there is no evidence that North Korea has yet mastered heat-shielding or reentry technologies necessary to deliver a nuclear payload to the United States.
North Korea's third nuclear test in February of 2013 is speculated to have moved it toward development of miniaturization capabilities necessary to place a nuclear weapon on a missile, but there are differences in U.S. intelligence estimates regarding how close North Korea might be to achieving this goal.
Regarding the Korean peninsula, both Defense Secretary Chuck Hagel and Commander of U.S. Forces Korea Curtis Scaparrotti have recently reaffirmed their commitment to a strong U.S. military presence there as a deterrent to North Korea. U.S. military presence in South Korea is currently in a period of transition: troops stationed in Seoul are being transferred to Pyeongtaek, a base slightly further south, defense sharing costs are being renegotiated, and Seoul is slated to regain wartime operation control in late 2015.