WASHINGTON – President-elect Barack Obama took center stage in the economic crisis for the third day running Sunday as he dispatched aides to pitch his rapidly expanding stimulus plan on TV and announced plans to introduce his economic team today.

Appearing on the Sunday talk shows, his advisers indicated that the ambitious plan he announced Saturday to create 2.5 million public works and alternative-energy jobs, will be far more costly than previously discussed. Along with other possible steps to turn around the economy, it could cost the government as much as $700 billion.

That amount, more than the nation has spent over the past six years in Iraq, would rival the sum Congress committed last month to rescuing the country’s financial system. It would also be one of the biggest public spending programs aimed at jolting the economy since President Franklin Roosevelt’s New Deal.

And it would be four times the size of the $175 billion stimulus package Obama promoted as a White House candidate.

“The economy has gotten much worse since then,” Austan Goolsbee, a University of Chicago economist and top Obama adviser, told CBS News’ “Face the Nation.”

“This is as big of an economic crisis as we’ve faced in 75 years, and we’ve got to do something that’s up to the task of confronting that,” Goolsbee said.

Obama’s aides also did not dispute a New York Times report that fear of worsening the economy might lead him to postpone advancing a centerpiece of his campaign – a tax increase for people earning more than $250,000 a year.

REPUBLICANS OBJECT TO MORE SPENDING

Whether by design or necessity, Obama appeared to be using the deepening economic crisis to step to the forefront and seize the stage in order to reassure a nervous nation two months before he takes office.

Republicans quickly criticized the idea of such a vast new initiative, saying Congress should instead cut taxes to spur economic growth.

“Democrats can’t seem to stop trying to outbid each other – with the taxpayers’ money,” House Minority Leader John Boehner, R-Ohio, said in a statement. “We’re in tough economic times. Folks are hurting. But the American people know that more Washington spending isn’t the answer.”

But one prominent Republican, former Secretary of Treasury James Baker, suggested that Obama and President George W. Bush take the almost unprecedented step of sitting down and trying to work together to address the crisis.

With financial markets fluctuating and unemployment rising, Democrats want to push a stimulus package through Congress in January and have it ready for Obama’s signature when he takes office Jan. 20.

Obama’s scheduled news conference today and formal introduction of his top economic aides will be the fourth day he has revealed plans for the economy – in the process overshadowing the activities of lame-duck President Bush.

Chief Obama strategist David Axelrod acknowledged that the leak Friday of New York Fed chief Timothy Geithner as Obama’s treasury secretary was calculated to stem plunging stock markets.

ECONOMIC TEAM SET TO DEBUT TODAY

In addition to announcing Geithner’s appointment today, Obama was expected to name Lawrence Summers, treasury secretary under President Bill Clinton, as head of the National Economic Council.

Asked several times whether the price tag of Obama’s economic stimulus plan would be in the range of $500 billion to $700 billion, Axelrod said he was “not going to throw a figure out there.” But he finally told George Stephanopoulos on ABC News’ “This Week”: “I think he’s going to do what’s necessary. And I suspect you’re asking a question that you know the answer to.”

Others hinted at similar numbers Sunday. Obama adviser and former Clinton administration Labor secretary Robert Reich and Sen. Charles Schumer, D-N.Y., also called for spending in the range of $500 billion to $700 billion.

Transition officials would not confirm that they are considering spending of that magnitude, but they made clear that economic conditions are dire, and suggested Obama might be forced to delay his pledge to repeal President Bush’s tax cuts for the wealthy.

Last week, Goldman Sachs said it expects the economy to shrink even faster by the end of the year, at a 5 percent annualized rate. Meanwhile, the Dow Jones industrial average dropped 5.3 percent for the week, and the nation’s largest bank, Citigroup, sought government assistance to avoid collapse.

While Obama has set a goal of creating or preserving 2.5 million jobs by 2011, his economic team – whose members are scheduled to be formally introduced at a news conference today in Chicago – have yet to decide how that would be accomplished or how much it would cost.

The plan would include new funding for public-works projects to repair the nation’s crumbling infrastructure, as well as a fresh infusion of cash to promote green technology. It also would include tax cuts for working families, students, seniors and job-creating businesses that Obama touted in his campaign.

The Washington Post contributed to this report.