Senator Orrin G. Hatch, the Republican finance committee chairman, is a critical voice on tax issues in Congress and support from him could make the difference in whether members of Congress fall in line and support the president’s proposal.

Republicans in Congress have generally been against tax cuts that add to the deficit. But many argue that now is the party’s opportunity to bring sweeping and enduring changes to the tax code.

“I’m open to getting this country moving,” Mr. Hatch said. He said that if the tax cut could stimulate the economy, then he was not as bothered by the impact it had on budget deficits. “I’m not so sure we have to go that route, but if we do, I can live with it,” Mr. Hatch said.

The comments came as Republican congressional leaders were preparing to huddle with President Trump’s economic team ahead of the administration’s rollout of its tax plan on Wednesday. Mr. Trump has told his staff that he wants to slash the corporate tax rate to 15 percent from 35 percent even if doing so increased the federal budget deficit.

Mr. Hatch, of Utah, said that he was not sure how the Congressional Budget Office would analyze the corporate tax plan that Mr. Trump is expected to propose. Republicans are planning to rely on “dynamic scoring” that accounts for economic growth created by the tax cuts to show that they would not increase the deficit.

“Whether 15 percent is the right figure or not, that’s something to be determined,” Mr. Hatch added.

Mr. Hatch had expressed skepticism on Monday about such a low corporate tax rate because, under the Senate’s reconciliation rules, changes to the tax code that reduce tax revenue expire after 10 years. Republicans are looking to use this maneuver to pass legislation with a simple majority that does not need to rely on votes from Democrats.