The U.S. military has drafted a document that calls for nuclear strikes against nations or terrorist groups to prevent them from using weapons of mass destruction against the United States or its allies.

The document ("Doctrine for Joint Nuclear Operations") was drafted in March.  It updates a 1995 version from the Clinton administration to reflect President Bush's doctrine of pre-emptive military strikes against nations or groups posing a threat to the United States.

The document outlines a number of scenarios for the use of nuclear weapons, which would require the approval of the president.

The revised draft has yet to become official policy.

The document envisions the use of earth-penetrating nuclear weapons to destroy deeply buried weapons.  The Bush administration has been looking to develop the so-called "bunker-busters," but U.S. Congress stopped funding the program last year.