Congress' efforts to fund highway spending with taxes on corporate earnings currently stashed overseas are "gaining momentum," Paul Ryan said Thursday.

Ryan, the chairman of the powerful tax-writing House Ways and Means Committee, said at a breakfast event hosted by Politico in Washington that he was optimistic about a deal to reform international taxation that would include a one-time surge of revenues from deferred taxes of multinationals' earnings.

Such a deal isn't possible in the next two weeks before the highway trust fund is expected to be exhausted, the Wisconsin Republican said, and Congress will have to pass a short-term funding patch through the end of the year.

But the agreement on taxing overseas earnings announced Wednesday by Sens. Rob Portman, R-Ohio, and Chuck Schumer, D-N.Y., "gives me a bit of hope" that a six-year infrastructure funding deal can be reached, he explained.

The agreement between Portman and Schumer would get rid of the current U.S. practice of taxing all overseas earnings at the U.S. corporate tax rate of 35 percent, the highest among advanced economies. It would replace that with a territorial system, similar to those of most major countries, in which foreign earnings are mostly untaxed.

Such a reform is necessary, Ryan said, to prevent U.S. companies from trying to move their headquarters or business operations in order to lower their taxes. Foreign takeovers and corporate "inversions" have increased in recent years largely thanks to the U.S. tax code.

As part of the transition to the new system, the Portman-Schumer plan would tax the estimated $2.3 trillion in U.S. multinational earnings currently reinvested overseas at an unspecified special lower rate. Ryan, with most Republicans, believes that the revenues that would result from such a "deemed repatriation" do not represent a tax hike if they come as part of reform of the international tax system, since the firms would have faced the 35 percent rate under the old regime if they ever repatriated the profits.

Ryan said that the plan, endorsed by the likely future Senate Democratic leader Schumer, tracks with what Republicans would like to do on international taxes and is "the essence of what it could look like."

In the meantime, he is working on building support for a funding source to replenish the highway trust fund through the end of the year to give Congress enough time to come to an agreement on a long-term plan involving revenues from repatriation. As for where the funds for the patch might come from, he said, "stay tuned."