The Obama administration will formally unveil a new policy on Tuesday restricting U.S. use of nuclear arms, renouncing development of new atomic weapons and heralding further cuts in America’s stockpile.

But even as President Barack Obama limits the conditions under which the United States would resort to a nuclear strike, he is making clear that nuclear-defiant states like Iran and North Korea will remain potential targets.

“I’m going to preserve all the tools that are necessary in order to make sure that the American people are safe and secure,” Obama told The New York Times in an interview that previewed his revamped nuclear strategy.

The policy shift, calling for reduced U.S. reliance on its nuclear deterrent, could build momentum before Obama signs a landmark arms control treaty with Russia in Prague on Thursday and hosts a nuclear security summit in Washington next week.

But it is also likely to draw fire from conservative critics who say his approach is naive and compromises U.S. national security.

The Nuclear Posture Review is required by Congress from every U.S. administration but Obama set expectations high after he vowed to end “Cold War thinking” and won the Nobel Peace Prize in part for his vision of a nuclear-free world.

Under the new strategy, the United States would commit for the first time not to use nuclear weapons against non-nuclear states that are in compliance with the Nuclear Non-Proliferation Treaty, even if it is attacked with biological or chemical weapons, according to The New York Times and a U.S. official who confirmed the details.

Those threats, Obama said, could be deterred with “a series of graded options” — a combination of old and newly designed conventional weapons.

Obama insisted “outliers like Iran and North Korea” that have violated or renounced the treaty would not be protected.

ROLLING BACK BUSH-ERA POLICY

Still, Obama is rolling back the Bush administration’s more hawkish policy set out in its 2002 review threatening the use of nuclear weapons to preempt or respond to chemical or biological attack, even from non-nuclear countries.

An exception under Obama’s plan would allow an option of reconsidering the use of nuclear retaliation against a biological attack if there is reason to believe the United States were vulnerable to a devastating attack.

To set an example for global arms control, Obama’s strategy — another departure from Bush-era policy — commits the United States to no new atomic arms development, U.S. officials said.

The United States will, however, increase investment in upgrading its weapons infrastructure, which one White House official said would “facilitate further nuclear reductions.”

Arms control experts see potential for significant cuts in the U.S. stockpile by upgrading weapons laboratories to weed out older, ineffective warheads.

Obama now faces the challenge of lending credibility to his arms control push while not alarming allies under the U.S. defence umbrella or limiting room to manoeuvre in dealing with emerging nuclear threats from Iran and North Korea.

The review is a test of Obama’s effort to make controlling nuclear arms worldwide a signature foreign policy initiative. It is also important because it will affect defence budgets and weapons deployment and retirement for years to come.

The strategy was developed after a lengthy debate among Obama’s aides and military officials over whether to declare that the United States would never be the first to use nuclear weapons in a crisis but would act only in response to attack.

Obama appeared unlikely to go as far as forswearing the first-strike option, which will disappoint some liberals.

The review comes a day before Obama leaves for Prague, where he and Russian President Dmitry Medvedev will sign a new START pact to slash nuclear arsenals by a third.

The signing ceremony will occur nearly a year after Obama’s Prague speech laying out his vision for eventually ridding the world of nuclear weapons. Obama acknowledged it might not be completed in his lifetime.

(Additional reporting by Caren Bohan, Phil Stewart and Tabassum Zakaria; editing by Chris Wilson)