>The strategy suggests that the United States might retaliate with a nuclear strike in response to a nuclear, chemical, or biological attack on the United States, U.S. troops, or friends and allies. “The United States will continue to make clear that it reserves the right to respond with overwhelming force—including through resort to all our options—to the use of WMD,” the strategy warns. Previous administrations have made similar statements at various times despite a long-standing policy not to use nuclear weapons against non-nuclear-weapon states unless they attack the United States in alliance with a nuclear-weapon state.

>Neither the threat to act pre-emptively nor to possibly react to a chemical or biological attack with nuclear weapons are novel, but the Bush administration has more openly and frequently discussed these options than its predecessors and has now set them out as official policy.

Sure, that's not the same thing as saying "we will definitely nuke you if you gas us", but you're never going to see something like that in writing because it removes the option of not doing it.