President Obama on Wednesday plans to propose a major overhaul of the nation’s corporate tax code, an election-year gambit that is likely to draw a contrast over a key policy issue with the Republicans vying to replace him.

Obama will propose lowering the nation’s tax rate to 28 percent. At the same time, however, he will seek to increase the amount of revenues raised overall through corporate taxation by eliminating numerous deductions and loopholes that save companies tens of billions of dollars a year on their tax bills, according to a senior administration official.

Today, the U.S. corporate tax rate of 35 percent is one of the highest in the world, but an abundance of loopholes and deductions means that many companies pay far less than that — or nothing at all. Companies in the United States pay almost half the taxes than companies do in other rich countries, compared to the size of the economy, according to the Organization for Economic Cooperation and Development.

In his proposed rewrite, Obama will target oil and gas companies for tax hikes while promising special breaks for manufacturing companies, according to a senior administration official.

The prognosis for the plan in Congress, which would have to sign off on the proposals, is unclear. Many Republicans, including the leading presidential candidates, have favored reducing taxes on businesses well below what Obama is proposing.

Former Massachusetts governor Mitt Romney, who has called for a 25 percent tax rate for corporations, is planning to deliver a speech on tax reform later this week, while his rivals for the GOP nomination have advocated tax rates half that.

Despite those disagreements, Republicans and Democrats have expressed broad support for a tax strategy that reduces rates across the board while eliminating special interest loopholes.

Treasury Secretary Timothy F. Geithner is planning to lay out the full details of the plan shortly before noon on Wednesday.

“We are going to propose a broad reform that will lower rates, broaden the base and eliminate and wipe out a very substantial fraction, dozens and dozens and dozens of special tax preferences for businesses,” Geithner said in congressional testimony last week. “We’re doing that because we think there’s a compelling economic case for doing that.”

Obama’s plan to raise additional tax revenue through corporate tax reform is notable because officials had previously suggested that they were hoping that corporate tax reform would neither add to, nor subtract from, annual budget deficits.

Now officials are counting on corporate tax reform to make a modest but still significant contribution to deficit reduction, part of a pattern of Obama adopting a more assertive stance toward raising taxes to help keep spending and revenues in check.

Though he has called for higher taxes on the rich, Obama has not offered a detailed blueprint for overhauling the personal income tax code, which is also full of loopholes and deduction. Such a blueprint is not expected to come before the November presidential election.

The corporate tax plan will include a minimum tax that must be paid by American multinational corporations on their foreign earnings — to prevent firms from sheltering profits oversees. Obama has also proposed ending tax breaks for companies that outsource and giving new tax incentives to firms that move jobs back home.

The corporate tax reform proposal has been a pet project of Geithner’s for over a year and a half. Last year, the Treasury completed a detailed white paper on corporate tax reform, but it was put on the back burner amid the acrimonious debate in Washington over the federal debt.