US plans for first strikes

His administration has released a strategy document which says it would prefer to act with the support of the international community, but if this is not possible it is prepared to act alone.

The document goes on to say that the US will use its position to spread freedom and prosperity around the world.

The BBC's Rob Watson, in Washington, says it is the most aggressive statement of US foreign policy since the Reagan era.

"The gravest danger our nation faces lies at the crossroads of radicalism and technology," the document states.

"As a matter of common sense and self-defense, America will act against such emerging threats before they are fully formed."

The policy paper fleshes out the new thinking first articulated by Mr Bush earlier this year - and the doctrine could face its first test if the US goes to war against Iraq.

Pre-emptive strikes

Although the document refers to the importance of working with allies and international organisations, it says the US will not hesitate to act alone, and pre-emptively, to exercise its right to self-defence.

On weapons of mass destruction, the document says the administration favours a policy of counter-proliferation, eliminating threats before they are unleashed.

The document also commits Washington to maintaining the absolute military supremacy of the United States.

It promises that American forces will be strong enough to deter any other nation from even attempting to match them.

Though proclaiming America's economic and military dominance, the document does contain an insistence that this power will not be used for unilateral advantage.

Instead, the stated aim is to spread freedom and prosperity throughout the world. And there are promises of increased aid to the developing world.

But the document also singles out China, warning about its military expansion.

"In pursuing advanced military capabilities that can threaten its neighbours in the Asia-Pacific region, China is following an outdated path that, in the end, will hamper its own pursuit of national greatness," it says.

Our correspondent says that to some countries, it is likely to confirm their worst fears of American cultural and political imperialism.

But to administration officials, the document follows in a tradition of the US being a shining light to the rest of the world.

The BBC's defence correspondent, Jonathan Marcus, says the new strategy largely turns its back on notions such as containment and deterrence that served America well during the Cold War.

He also says it reflects the mindset of the more hawkish military camp inside the Bush administration, personified by Defence Secretary Donald Rumsfeld.