From the source:
"[T]he United States will not use or threaten to use nuclear weapons against non-nuclear weapons states that are party to the NPT [Non-Proliferation Treaty] and in compliance with their nuclear non-proliferation obligations. ...
"The United States would only consider the use of nuclear weapons in extreme circumstances to defend the vital interests of the United States or its allies and partners.
"[T]he United States affirms that any state eligible for the assurance that uses chemical or biological weapons against the United States or its allies and partners would face the prospect of a devastating conventional military response – and that any individuals responsible for the attack, whether national leaders or military commanders, would be held fully accountable." (italics added)
