WASHINGTON – President Barack Obama this week takes his 2012 reelection bid cross-country, to the airwaves and to Facebook, pushing a prescription for long-term US fiscal health that includes tax hikes on the richest Americans.

Obama, whose audacious 2008 White House bid leaned heavily on social networking sites, will hype his "Shared Responsibility and Shared Prosperity" plan at Facebook's Palo Alto, California headquarters on Wednesday.

"I hope you'll take a break from either friending or defriending each other to RSVP at facebook.com/whitehouse," he joked in a video posted online Monday.

The US president's campaign-style blitz came as Republicans redoubled their attacks on his handling of the struggling US economy and promoted their "Path to Prosperity" blueprint for reining in the country's galloping deficits.

And ratings agency Standard & Poor's cut the outlook on US sovereign debt to "negative" Monday, sending stocks plunging as it doubted Washington's ability to tackle its huge debt and fiscal shortfalls.

"As S&P made clear, getting spending and our deficit under control can no longer be put off for another day," warned Republican House Majority Leader Eric Cantor. "Serious reforms are needed to ensure America's fiscal health."

Obama has agreed on the need for spending cuts while warning against trimming investments in education or infrastructure, and emphasizing that the wealthiest Americans could stand to pay more in taxes.

"People like me don't need another tax cut," he said in his weekly address on Saturday as Americans raced to file their taxes by a Monday deadline.

In his travels, Obama will "speak directly to the American people about his vision for reducing our debt and bringing down our deficit, based on the values of shared responsibility and shared prosperity," the White House said.

Obama was to preview his message in interviews with television stations from Colorado, Indiana, and North Carolina -- key battleground states he won in 2008 -- as well as Texas, then do a "town hall" question-and-answer session in Virginia on Tuesday.

On Wednesday, he was off to Palo Alto, and a day later to Reno, Nevada, another battleground.

Obama had cited Facebook in his January State of the Union speech as an example of innovative US companies that can help the world's richest country overcome its dreary present economic circumstances and "win the future."

The US president has taken pains to contrast his vision with Republican calls to slash government spending and roll back regulations while lowering tax rates on the richest Americans and corporations.

In public speeches and exhortations to supporters behind closed doors, Obama has made Republican House Budget Committee Chairman Paul Ryan's blueprint for cutting some $4.4 trillion from the deficit over 10 years into a political punching bag some 18 months before the November 2012 elections.

Obama -- who says his approach will slice some $4 trillion in 12 years or less -- has notably accused Ryan of looking to gut the Medicare and Medicaid programs for the elderly and the poor.

The message could resonate among older voters, who went for Republicans by a 59-38 percent margin when the party routed Obama's Democrats last November, retaking the House of Representatives and posting gains in the Senate.

At the same time, a public opinion poll released Monday by the Gallup organization showed 59 percent of Americans said the rich pay too little in taxes, against 25 percent who say they pay the right amount and 13 percent who say the wealthy are overtaxed.

Obama struck a deal with Republicans in December to extend by two years tax cuts on all Americans that had been set to expire come January, at the cost of extending cuts that only reach the wealthiest.

Since then, he has warned the United States "can't afford" making upper-bracket cuts permanent and said "it's not a matter of punishing their success. It's about promoting America's success."