<P> National Command Authority (NCA) is a term used by the Department of Defense of the United States of America to refer to the ultimate source of lawful military orders . The NCA comprises the President of the United States (as commander - in - chief) and the Secretary of Defense jointly, or their duly deputized successors, i.e. the Vice President and the Deputy Secretary of Defense . The term also refers to communications with the commanding officers of the Unified Combatant Commands to put U.S. forces into action . </P> <P> Only the President can direct the use of nuclear weapons by U.S. armed forces, including the Single Integrated Operational Plan (SIOP). While the President does have unilateral authority as commander - in - chief to order that nuclear weapons be used for any reason at any time, the actual procedures and technical systems in place for authorizing the execution of a launch order requires a secondary confirmation under a two - man rule, as the President's order is subject to secondary confirmation by the Secretary of Defense . If the Secretary of Defense does not concur, then the President may in his sole discretion fire the Secretary . The Secretary of Defense has legal authority to approve the order, but cannot veto it . </P>

Who has the power to launch nuclear weapons in the us