By Steve Schifferes BBC News Online Washington correspondent

The president, who gave his annual State of the Union address to Congress, must convince an increasingly sceptical American public, and many of the US's allies overseas, that Iraq is not co-operating with the UN weapons inspectors, and presents a clear and present danger to the United States.

[The president] shall from time to time give to the Congress information of the State of the Union, and recommend to their consideration such measures as he shall judge necessary and expedient US constitution

Click here for more about the State of the Union address

While the US military build-up in the Gulf continues, a frantic round of diplomacy is under way to try to convince the UN Security Council to back a second resolution authorising force after the report of chief UN weapons inspector Hans Blix.

But the most important battle will be the battle for public opinion.

Democrats have already complained that without providing full evidence that Iraq still has weapons of mass destruction, any premature move to military action could alienate US allies.

Real disarmament

The Bush administration believes that Iraq has already demonstrated that it is not engaged in real disarmament, and continues to conceal thousands of chemical and biological weapons or agents.

Thousands of US soldiers are already stationed in the Middle East

But at this delicate stage, the president is unlikely to give a precise timetable for war.

However, hardliners like former assistant secretary of defence Richard Perle would like the president to go further than just discussing the evidence, and spell out the broad rationale behind the new US security strategy.

In Mr Perle's view, the US should make explicit that it is abandoning its "globalist" perspective of the Clinton years which failed to tackle state-sponsored terrorism.

Instead, he should make it clear that the US is prepared to lead a "posse" of "like-minded liberal democracies" to make the world unsafe for terrorists and those who possess weapons of mass destruction, whether its European allies co-operate or not.

And Mr Perle hinted that North Korea - which the US says has admitted having a programme aimed at making nuclear weapons - should be the next target after the US has dealt with Iraq. Domestic agenda

President Bush also made the case for pursuing his vision of "compassionate conservatism," and much of the State of the Union speech will be devoted to spelling out his domestic priorities.

President Bush is seeking to reform health spending

Since the Republicans regained full control of both Houses of Congress in November, Mr Bush will have a chance to implement his ambitious agenda of tax cuts and healthcare reform.

The US economy has slowed, and unemployment has risen sharply in the past six months, while uncertainty about a war in Iraq is exacerbating the situation.

The president argues that his tax cut, which would eliminate taxes on dividends paid by companies to individuals, at the cost of $692bn over 10 years, will stimulate investment and create jobs.

But Democrats say that further tax cuts will put an intolerable strain on the Federal budget deficit, already at record levels, and fail to put money in the pockets of people who will spend it.

Senate Democratic leader Tom Daschle said - in a pre-emptive strike - that "the state of our union is anxious."

Reforming healthcare

President Bush will begin a drive for an ambitious plan to curb the costs of one of the fastest-growing and popular entitlement programmes, Medicare, which pays hospital and doctors' bills for the elderly.

The huge US healthcare system is failing to provide coverage to large numbers of people, and senior citizens have long complained about the lack of any help to pay for the cost of prescription drugs.

But the president said that any new benefit must be linked to reform, which would place Medicare patients in health maintenance organisations which would exercise more control over costs.

President Bush has a narrow majority at home, and faces significant opposition abroad, for his proposals.

But so far he is not letting that deter him from trying to move quickly to implement his plans.

If he succeeds, this State of the Union could well prove the defining moment of his presidency.