(CNBC) -- U.S. companies won't tolerate failure on corporate tax reform, House Speaker Paul Ryan said Wednesday.
"We've already seen a rash of inversions," the Wisconsin Republican said on CNBC, referring to the practice of U.S. companies merging with foreign firms in lower tax countries, and then redomiciling there.
"[If] we don't get this done, those companies sitting back and waiting for us to fix this tax code are going to leave," he predicted on "Squawk Box."
Ryan's comments came as the House and Senate work on separate tax overhaul plans in hopes of passing a bill for President Donald Trump to sign by year-end.
In a CNBC interview last week, top Trump economic advisor Gary Cohn also warned about inversions.
The director of the National Economic Council, who used to be the No. 2 executive at Goldman Sachs, said, "Look, a year ago, I was on the other side of this equation. I was advising companies how to get out of the burdensome U.S. tax system. We were talking about inversions; we were talking about moving companies out of the United States."
In light of his current role in the administration, Cohn said he does not regret his efforts at Goldman. "I didn't feel guilty because boards have a fiduciary responsibility to their shareholders. That's what they're supposed to do. So, you know what? We're going to make America competitive. We're going to make it compelling for people to build their companies in America."
In Wednesday's CNBC interview, Ryan made the case for how to create a more attractive business environment in America. He cited three main corporate tax changes, including cutting the federal rate from 35 percent to 20 percent; allowing immediate "full expensing" of capital expenditures; and switching to a "territorial system" that would not subject American companies to U.S. taxes on foreign earnings.
The current "worldwide system" in the U.S., which requires companies to pay U.S. taxes on earnings wherever they are generated, penalizes American companies that want to bring foreign income back home, Ryan said.
"They basically don't as a result. That's why we have $3 trillion in cash parked overseas in the first place," Ryan said. "Unlocking that brings that money home. But unlocking that also puts us on a better level playing field."
In addition to a move to a "territorial system," the House approach proposes a one-time "tax holiday" rate of 12 percent on cash returns and 5 percent on non-cash repatriated from overseas.
"When you combine 'full expensing,' which will be effective immediately, with a rate cut, with repatriation, it says the incentive is to invest in America," Ryan said. "Getting from the last of the country pile, meaning the highest industrial world tax rate, to one of the best tax rates, we really are convinced that that's going to give us faster economic growth and higher wage growth."