Under a plan baked into the White House’s budget for 2016, U.S. corporations would theoretically be forced to pay hundreds of billions in new taxes on money kept abroad.

Levying fees on the $2.1 trillion in funds largely held by shell companies through an accounting trick called deferral, the move, which President Barack Obama announced last month, is aimed at raising cash for desperately needed public works programs and infrastructure improvements. If he is successful, companies would no longer have a legal way of avoiding the 35 percent corporate tax by indefinitely investing funds outside the U.S.

But analysts say it’s unlikely such a tax haven windfall will materialize, because it depends on being included in budget legislation drafted and passed by a Republican-controlled Congress. In that sense, the proposal — part of a larger fiscal document outlining where the White House stands on important questions — is seen as a starting gambit in tax reform negotiations.

Republican politicians have vowed to scupper the plans when they come before Congress, where the GOP has a four-seat majority in the Senate and overwhelming control of the House after midterm elections last year from which they emerged victorious and emboldened.

"For six years the president has pursued higher taxes and higher spending, and our economy has paid the price. This budget is simply more of the same,” said House Ways and Means Committee Chairman Paul Ryan, R-Wis.

Yet behind such a stance lie powerful business interests that have long stored cash offshore rather than paying U.S. taxes. Representing hundreds of multinational companies, the U.S. Chamber of Commerce and Business Roundtable successfully defended against more modest tax reforms in Obama’s first term.

The Chamber, which spent $33 million for Republicans and against Democrats in the last election cycle, described his budget as “more spending, more taxes, more debt.”

Hundreds of billions in tax revenue are avoided through deferrals. Firms such as General Electric — which has reportedly avoided paying much U.S. tax in the past through a combination of creative accounting and aggressive lobbying — have figured prominently in the precipitous decline in the share of federal revenue paid by corporations, from about 30 percent in 1950 to 10 percent a half-century later.

Many Fortune 500 companies dedicate whole departments to minimizing their tax burden, taking advantage of tax breaks that critics slam as corporate welfare and loopholes that allow for storing capital overseas.