Doctrine for Joint Nuclear Operations
The Pentagon's Doctrine for Joint Nuclear Operations mentions the possiblity of an American nuclear pre-emptive strike.
From the New York Times:
The plan is undergoing final review by the Pentagon's joint staff and by Secretary of Defense Donald H. Rumsfeld, and it could be finished in the next several weeks, according to a Pentagon official. The document was first reported by The Washington Post.
A Pentagon official confirmed that a copy of the document posted on the national security Web site GlobalSecurity.org was authentic.
The Bush administration said in 2002 that a pre-emption strategy was necessary to deal with emerging threats from terrorist groups seeking unconventional weapons and from the proliferation of nuclear capability to numerous countries.
Although the unclassified document reasserts the longstanding American position that it will not make definitive statements about when nuclear weapons will be used, it describes several scenarios for using them, including circumstances under which pre-emptive use might be necessary.