The Pentagon's new blueprint on nuclear forces has raised the question whether the Bush administration is lowering the threshold for using nuclear arms. In its Nuclear Posture Review, the Pentagon cites the need for new nuclear arms that could have a lower yield and produce less nuclear fallout. The weapons, the Pentagon said, could be designed to destroy underground complexes, including stores of chemical and biological arms. The targets might be situated in Iraq, Iran, Syria, Libya or North Korea, a reorientation away from cold war scenarios involving Russia.