Republican lawmakers are looking to tax the $2 trillion in earnings that U.S. companies hold overseas as a way to fund roads and bridges.

With the prospects for a broad revamp of the tax code dimming, lawmakers are looking to the exhaustion of the highway trust fund next month as a crisis that could prompt Congress to rewrite at least part of the tax code pertaining to international taxation.

The enticement is the $2 trillion-plus in untaxed overseas earnings that could be repatriated and taxed, enough to make up the highway funding shortfall for a long time.

"A lot of people are talking about this in the context of tax reform," Sen. Rob Portman, R-Ohio, said Wednesday, speaking at a conference put on by the law firm BakerHostetler in Washington.

Portman, a member of the tax-writing Senate Finance Committee, is one of several lawmakers on both the Right and Left who have expressed interest in a deal related to the highway fund in recent days.

Their comments reflect an acknowledgment that a deal on overall tax reform that would lower rates while broadening the tax base is not doable in the 114th Congress. President Obama had sought a reform for business taxation, and the GOP chairmen of the tax committees expressed interest in working toward that goal. But the effort was slowed by the difficulty of including the thousands of businesses that file through the individual side of the tax code.

Speaking at the same conference Wednesday, Sen. Roy Blunt, R-Mo., said that admitting defeat on the push for tax reform would be crucial to getting smaller legislation done.

"The first thing that has to happen is some recognition that we're not going to have overall tax reform in this Congress with this president," Blunt said. He explained that "until you get there, there's always this great desire to keep everything off the table that you want to keep on the table for the big deal. It's important to realize that, that big deal is not going to occur."

Blunt's words, which echoed comments by Senate Majority Leader Mitch McConnell over the weekend, are not likely to be well-received by businesses. Business groups have pushed hard for business tax reform, saying that the country's 35-percent statutory corporate tax rate, the highest among advanced economies, harms their competitiveness.

Another critical flaw of the U.S. corporate tax code is that it encourages companies to keep foreign earnings overseas. The government taxes companies on overseas earnings at the 35 percent rate, granting a credit for taxes paid to foreign governments, but only if that money is repatriated to the U.S.

The result is that companies have roughly $2 trillion in unrepatriated earnings abroad.

Changing the international tax system to tax those earnings could be "one of the potential sources of how we close the gap between what the gas tax will provide and reasonable expectations for what our transportation system should do," Blunt said Wednesday.

That gap, according to the Senate Budget Committee, is $175 billion over the next 10 years. The highway trust fund is dedicated to road and bridge construction projects, but has needed transfers from the general budget in recent years as the value of the gas tax has declined due to inflation and fuel-efficient cars have cut into gas use.

Finding a way to make up the difference and keep up construction and maintenance is a source of motivation for lawmakers.

Rep. Paul Ryan, chairman of the House Ways and Means Committee with jurisdiction over taxes, indicated on Tuesday that he was looking for a deal related to international tax laws.

"The question is: Can we take a couple of steps in the right direction, particularly with international tax laws and international tax rules?" the Wisconsin Republican said in an appearance on Bloomberg TV.

Rep. Kevin Brady, R-Texas, another member of the committee, said Tuesday that Ryan was looking for deals with Democrats on international taxation, among other items. "Just push into the fog to see who might want to advance things," he said.

Democrats, including Sen. Ben Cardin of Maryland and Rep. Xavier Becerra of California, expressed interest in such a deal at the conference Wednesday.

"There's talk that to get tax reform you have to do the transportation bill, and we may use some of the revenues you get from tax reform, at least on the international level, to maybe do something on the transportation side," Becerra said.