Lawrence DiRita, the Pentagon spokesman, said the document was taken down "because even in an unclassified world this is not the kind of thing you want flying around the Internet."

Entitled "Doctrine for Joint Nuclear Operations" and prepared under the direction of the chairman of the Joint Chiefs of Staff, the draft was spotted on a Pentagon website earlier this month.

DiRita said the results of the review have not yet gone to either Defense Secretary Donald Rumsfeld or General Richard Myers, the chairman of the Joint Chiefs of Staff.

"It's getting reviewed in the normal order of things. It hasn't made it to any level at which any decisions would be made," he said.

"It would be premature to discuss changes to US posture in this regard because it is not at the level at which decisions are made," he said.

The review was initiated in response to a broader review of the US nuclear posture in 2001 that called for a smaller but more flexible nuclear force in the face of a more uncertain threat environment.

"To maximize deterrence of WMD (weapons of mass destruction) use, it is essential US forces prepare to use nuclear weapons effectively and that US forces are determined to employ nuclear weapons if necessary to prevent or retaliate against WMD use," the draft document said.

The document gives examples of conditions under which US combatant commanders may request presidential approval for the use of nuclear weapons.

They include an adversary using or planning to use weapons of mass destruction against US or allied forces as well as civilian populations.

Nuclear strikes could be employed against an imminent biological weapons attack that only nuclear weapons could "safely" destroy, according to the draft.

They also could be used to destroy deep, hardened bunkers containing enemy chemical or biological weapons or the command and control infrastructure required to execute a chemical, biological or nuclear attack.

A number of scenarios envision nuclear strikes even without enemy weapons of mass destruction in the equation.

They could be used, for instance, to counter potentially overwhelming conventional adversaries, to secure a rapid end of a war on US terms, or simply "to ensure success of US and multinational operations," the document indicated.

In the context of the US-led "war on terror", the draft suggests that states that provide surrogates with weapons of mass destruction could themselves be targeted with US nuclear strikes.

Regional US commanders may request presidential approval to go nuclear "to respond to adversary-supplied WMD use by surrogates against US and multinational forces or civilian populations," it said.

If approved, the draft would give the green light to deploy nuclear weapons to parts of the world where they might be used and urges troops to constantly train for nuclear warfare.