The United States unveiled Tuesday the long-anticipated new nuclear strategy, promising to reduce the role of nuclear weapons in U.S. national security strategy while reaffirming extended deterrence commitments to its allies.

The document, which establishes U.S. nuclear policy, strategy, capabilities and force posture for the next five to ten years, marks a break with the Bush-era nuclear doctrine that in fact lowered the threshold of usage of nuclear weapons and weakened the international non-proliferation regime.

Conditional no-use of nukes

The United States will not use or threaten to use nuclear weapons against non-nuclear weapons states that are party to the Nuclear Non-Proliferation Treaty and in compliance with their nuclear non-proliferation obligations, U.S. Secretary of Defense Robert Gates said in a joint briefing with Secretary of State Hillary Clinton and Secretary of Energy Steven Chu on the newly released strategy, known as Nuclear Posture Review (NPR).

This conditional assurance means that countries like Iran and the Democratic People's Republic of Korea that have violated or renounced the treaty would remain on the potential target list of U.S. nuclear forces.

Gates also warned that "if any state eligible for this assurance were to use chemical or biological weapons against the United States or its allies or partners, it would face the prospect of a devastating conventional military response."

This no-use strategy is not only limited by preset conditions, but also could be revised under certain circumstances.

"Given the catastrophic potential of biological weapons and the rapid pace of bio-technology development, the United States reserves the right to make any adjustment in the assurance that may be warranted by the evolution and proliferation of the biological weapons threat and US capacities to counter that threat, " said the document.

Compared with Bush-era threat of nuclear retaliation in the event of a biological or chemical attack, Obama administration's declaration of conditional no-use of nuclear forces could be regarded as significant progress in maintaining the non- proliferation regime.

But this new strategy still disappointed some progressives who argued that the U.S. should renounce the longstanding threat to use nuclear weapons first and declare unconditional no-use of nuclear arsenals against non-nuclear states, as some other major nuclear states have done.

Further disarmament

"The United States will pursue post-New START arms control with Russia that addresses not only strategic weapons, but also non- strategic and non-deployed nuclear weapons," said the new strategy.

The United States and Russia last month finalized a new nuclear disarmament deal to replace the expired Strategic Arms Reduction Treaty (START), agreeing to reduce their deployed nuclear warheads by 30 percent to 1,550.

Obama and his Russia counterpart Dmitry Medvedev are scheduled to sign the new START treaty on April 8 in the Czech capital of Prague, where the U.S. president formally unveiled his roadmap toward a world without nuclear weapons in April, 2009.

Reduced nuclear arsenal does not suggest that the U.S. will withdraw its commitment to its allies on the extended deterrence, also known as "nuclear umbrella."

The new strategy "reflects the Administration's commitment to strengthening deterrence against 21st century threats to the United States, our allies, and partners," according to the document. "The Administration is pursuing a comprehensive approach to broaden regional security architectures, including through missile defenses and improved conventional forces."