The United States announced this week a new strategic policy for its nuclear weapons that puts unprecedented emphasis on the nuclear threat from terrorists and rogue states, as opposed to traditional nuclear powers like Russia and China. Some analysts see the new policy as an important step in meeting the changing international situation. But critics call the move reckless and irresponsible.

The Nuclear Posture Review - the third since the end of the Cold War - limits the circumstances under which the United States would use nuclear weapons, with a long-term goal of achieving a nuclear-free world.

The Obama administration's new policy is a major departure from previous nuclear strategy. It seeks to defend the United States and its allies against terrorist organizations, which it sees as greater threats than countries like Russia and China that have large, decades old nuclear arsenals.

U.S. Secretary of Defense Robert Gates unveiled the new strategy at the Pentagon, saying it is driven by the changing nature of the security environment facing the United States.

"The review rightly places the prevention of nuclear terrorism and proliferation at the top of the U.S. nuclear policy agenda," said Gates. "Given al-Qaida's continued quest for nuclear weapons, Iran's ongoing nuclear efforts and North Korea's [nuclear and missile] proliferation, this focus is appropriate and, indeed, essential - an essential change from previous reviews."

Although the new policy is designed to reduce the role of nuclear weapons in America's security strategy, U.S. officials say it will not adversely affect the nation's ability to protect itself or its allies.

"For generations, the United States' nuclear deterrent has helped prevent proliferation by providing our non-nuclear allies in NATO, the Pacific, and elsewhere with reassurance and security. The policies outlined in this review allow us to continue that stabilizing role," said U.S. Secretary of State Hillary Clinton.

In a controversial move, the United States for the first time says it will not use atomic weapons against nonnuclear states that are in compliance with the Nuclear Nonproliferation Treaty, even if such countries attack the U.S. with biological or chemical weapons.

There is no such commitment for countries like Iran and North Korea, which the United States says have violated non-proliferation obligations, pursed missile development and defied the directives of the United Nations Security Council.

Tom Collina, Research Director for the Washington-based Arms Control Association, says the new policy is a positive step that will give countries an incentive to refrain from developing nuclear weapons.

"The point of this document is to build support among other nations in the world to help the United States in its campaign to stop weapons programs in North Korea and Iran," said Collina.

Other analysts are concerned the new strategy could have the opposite effect.

Matthew Bunn is a nuclear security and nonproliferation specialist at Harvard University.

"For hard-liners in Pyongyang or hard-liners in Tehran who want nuclear weapons, they now have a new argument," said Bunn. They can say, 'Look, the United States is almost explicitly saying that we are on their target list, so we should have nuclear weapons in order to deter any attack on us.' So that, I think, is an unfortunate addition to the ammunition of pro-nuclear weapons advocates in Pyongyang and Tehran," he said.

The new strategy states that America's atomic arsenal is poorly suited to address the challenges "posed by suicidal terrorists and unfriendly regimes seeking nuclear weapons."

Still, the United States will maintain its nuclear triad of intercontinental ballistic missiles, nuclear-capable aircraft and submarines.

Under the new strategy, the Obama administration will not develop new nuclear warheads or new capabilities for nuclear weapons - a move critics say will weaken the country's defense.

Frank Gaffney is President of the Center for Security Policy here in Washington.

""If the American people actually understand what is afoot, they will be horrified," he said. "I think the American people are going to be mad as hell at anybody who attacks this country with chemical or biological weapons and they are going to be very mad at any president of the United States that says, 'Oh we are not going to punish those who might do that in a way that, who knows, might have contributed to dissuading them from doing it in the first place.' This is reckless. This is irresponsible," Gaffney said.

Next week, the leaders of 47 countries are scheduled to visit Washington to discuss improvements in securing nuclear materials.

An international conference on strengthening the Nuclear Non-Proliferation Treaty is scheduled for May at the United Nations.