Making his debut to a joint session of Congress, Mr Obama will tell lawmakers "we will rebuild, we will recover", according to pre-released excerpts.

Mr Obama's first weeks in office have been marked by the passage of a $787bn (£545bn) economic stimulus plan.

Earlier, aides said he would offer a "sober assessment" of US prospects.

He will emphasise that his hard-fought stimulus bill - which includes efforts to save or create 3.5m jobs - will help restore growth, correspondents say.

Other initiatives in the first month of Mr Obama's presidency have included a banking bail-out and a plan to support homeowners struggling with mortgages.

'American qualities'

The BBC's Kevin Connolly in Washington says Tuesday's speech will look and feel like the State of the Union addresses which normally come at about this point in the political calendar.

But because Mr Obama is new to office, and therefore not in a position to take responsibility for the triumphs and disasters of 2008, this will be billed simply as an address to the joint houses, our correspondent adds.

According to the excerpt released several hours before Mr Obama was due to speak, the president will tell Congress and the American people that the country will overcome its current problems.

"But while our economy may be weakened and our confidence shaken; though we are living through difficult and uncertain times, tonight I want every American to know this: We will rebuild, we will recover, and the United States of America will emerge stronger than before."

"Those qualities that have made America the greatest force of progress and prosperity in human history we still possess in ample measure," Mr Obama will say.

"What is required now is for this country to pull together, confront boldly the challenges we face, and take responsibility for our future once more."

Mr Obama has said he will halve the budget deficit he inherited from the Bush administration by 2013 - a promise made despite his huge stimulus.

The package, signed after compromises debated in both houses, was designed to channel federal money toward infrastructure projects, health care, renewable energy development and conservation programmes.

Mr Obama's Treasury Secretary, Timothy Geithner, has also unveiled a comprehensive bank bail-out plan worth at least $1.5 trillion (£1.02 trillion).

For housing, the government has announced a plan to provide refinancing to four to five million "responsible homeowners" on the verge of defaulting.

Response

One of the president's aides, David Axelrod, said on MSNBC television a day ahead of his boss's speech: "The president has the theory that you treat Americans like adults and tell them where we are and where we need to go."

With many elements to the government's plans, there was a need for "aggressive action," he added.

"I think the bigger concern is to not be aggressive at a time when a tepid approach could really consign us to a long-term economic catastrophe."

The presidential address begins at 2100 (0200 GMT), with Republican Bobby Jindal delivering his party's response afterwards.

The 37-year-old governor of Louisiana - the first Indian-American to occupy such a post - is one of the Republican Party's rising stars, and is tipped as a likely contender for the White House four years from now.