WASHINGTON (MarketWatch) -- The United States can't afford an extension of Bush-era tax cuts for the wealthiest Americans, President Barack Obama said Wednesday, even as he called in a fiery campaign-style speech for tax breaks for middle-class Americans.

With his party bracing for losses in the midterm congressional elections, Obama laid out a series of economic proposals and took the fight over taxes directly to Republicans, who want to extend breaks for all earners.

"Let me be clear to [House Republican Leader John] Boehner and everyone else," said Obama at a community college in Parma, Ohio, across the state from Boehner's district. "We should not hold middle-class tax cuts hostage any longer. We are ready, this week, to give tax cuts to every American making $250,000 or less. See First Take commentary on Obama's targeting of Boehner.

"For any income over this amount, the tax rates would go back to what they were under President Clinton. This isn't to punish folks who are better off -- it's because we can't afford the $700 billion price tag." Read full text of Obama's speech.

Republicans are floating a tax freeze and a cut in government spending as Obama is also calling for a $50 billion plan to rebuild U.S. roads and railways, as well as a permanent extension of research tax credits and letting businesses write off 100% of their investments through 2011.

A White House spokesman said the proposals would be fair by closing unspecified corporate loopholes, including on oil and gas companies in particular.

Treasury Secretary Timothy Geithner said in a Wednesday interview on the cable channel CNBC that he believes there's support in Congress to get Obama's proposals through. The ideas have "very broad support," he said.

If the tax cuts expire, the current 25% marginal rate would go up to 28%; the 28% rate would go up to 31%; and the 33% rate would rise to 36%. About 16% of filers pay the current 25% rate, while just 1.2% pay the 33% rate.

U.S. stocks held modest gains Wednesday after Obama spoke and the Federal Reserve's Beige Book reported mixed or decelerating August conditions in five of the central bank's 12 districts. The Dow Jones Industrial Average closed up 46.32 points, or 0.5%. See Market Snapshot.

Obama's speech came with the midterm elections less than two months away, and as Republicans appear to be within striking distance of retaking the House of Representatives.

Before the president was scheduled to speak Wednesday, House leader Boehner proposed a two-year freeze on all current tax rates and a cut in non-security-related government spending back to 2008 levels. Read more about Boehner's plan.

Boehner said on ABC's "Good Morning America" that he's open to Obama's ideas but continued to hammer at the White House, saying that it's "out of touch" with voters and that Americans continue to ask, "Where are the jobs?"

Lawmakers will have little time to enact new proposals from either party when they return to Washington early next week. Members of Congress will be in session for less than a month before heading back to their districts to campaign. Read more on MarketWatch's election blog.

At the same time, some analysts are skeptical that Obama's proposals will do much good for the economy.

"While potentially helpful, we do not expect these proposals to have a large effect on growth," wrote Alec Phillips of Goldman Sachs, in a research note. The expanded research credit is too small to have much effect, he said.

Congressional Democrats are under increasing pressure as the Nov. 2 midterms draw nearer. The most recent Wall Street Journal/NBC News poll found that voters were split over which party they'd like to see control Congress after the elections but that Republicans have a 49%-to-40% advantage among those likely to vote.