In his speech to the joint session of the House of Representatives and the Senate, Mr Obama emphasised that his hard-fought stimulus bill - which includes efforts to save or create 3.5m jobs - will help restore growth.
This is America. We don't do what's easy. We do what is necessary and move this country forward
An era of extravagant spending must end, the president told Congress.
Outlining what he saw as the roots of the economic crisis, Mr Obama told congressmen that short-term gains had been prized over long-term prosperity.
"And all the while, critical debates and difficult decisions were put off for some other time on some other day," he said.
"Well, that day of reckoning has arrived, and the time to take charge of our future is here."
He praised Congress for passing the economic stimulus plan, which he said would create millions of jobs and revitalise the US, and deliver a tax cut to 95% of Americans by 1 April.
Obama: 'We will recover'
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.
The first month of Mr Obama's presidency has also included a banking bail-out worth at least $1.5 trillion (£1.02 trillion) and a plan to support "responsible homeowners" struggling with mortgages.
He won a standing ovation when he told his audience that banks and bankers taking public money would be fully accountable, vowing that tax dollars would not be frittered away.
"Those days are over," Mr Obama said. "It's not about helping banks, it's about helping people."
The speech came days before the unveiling of the administration's first budget, with sights set on reducing the giant US deficit, currently standing at about $1 trillion.
Mr Obama said the vast deficit and the "crushing cost" of healthcare made the need for wide-ranging reform more urgent than ever, and he pledged to reform and improve the nation's schooling and boost the numbers of students in higher education.
He restated a pledge made on Monday to cut the deficit in half by the end of his first term, and said officials had begun to go "line by line" through the federal budget "to eliminate wasteful and ineffective" schemes.
The BBC's Kevin Connolly in Washington says Barack Obama delivered a powerful address, offering more hope than in recent major speeches.
The address looks and feels like the State of the Union speech 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 was billed simply as an address to the joint houses, our correspondent adds.
While much of his speech focused on domestic issues, Mr Obama also touched on the key foreign policy issues facing his administration.
Reviews of US involvement in both Iraq and Afghanistan were currently ongoing, the president said, and would soon deliver their results.
The terrorists - in Obamaland - are lumped in with other problems the world faces: global warming, disease, etc
He promised a "new and comprehensive strategy" for Afghanistan and Pakistan aimed at defeating al-Qaeda and defeating extremism.
And while he paid tribute to US troops serving overseas, there was no detailed reference to plans for Iraq, or any reference to Iran, whose nuclear programme is viewed by many analysts as a major foreign policy challenge for the new president.
The speech came as some of the first polls analysing Mr Obama's level of public support indicated that voters still strongly back the man they chose for office fewer than four months ago.
A New York Times/CBS News poll published ahead of his speech put the president's approval rating at 63%, with a Washington Post/ABC News survey showing 68% support.
The presidential address - which began late and lasted a little over 45 minutes - was followed by a response from Republican Bobby Jindal.
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.
He was highly critical of Mr Obama's plans, dismissing the stimulus plan and banking bail-out as Washington waste.
"The way to lead is not to raise taxes and put more money and power in hands of Washington politicians," he said.
REACTION TO PRESIDENT OBAMA'S SPEECH
The economic crisis requires immediate, bold and comprehensive action. And on Tuesday night, Mr Obama displayed the ambition and the sweeping vision that won him the White House - and that this crisis demands. It was a refreshing change after his less-than-forceful handling of the stimulus bill.
The speech capped an often frantic start for his administration that has surpassed even the first month of FDR's New Deal. And for Obama, it was a chance to step back and spell out the full scope of the challenges facing the nation — and connect the dots of his economic plan for moving ahead.
Well, this was an extraordinary speech. We certainly do have a new president. My own reaction was that Obama looked stronger and more confident tonight than I have ever seen him before - and he has never lacked for confidence in the past.
Well, the problem for Republicans is that, (a), Americans support Obama's tax plan as laid out during the campaign. (b), Americans are demanding more government involvement. Remember October 2008: the specter of socialism, as dredged up by the GOP, failed. And the problems weren't as bad as they are now!
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