Representative Kevin Brady, Republican of Texas and the chairman of the House Ways and Means Committee, said in a statement on Friday that “our economy produced solid growth last quarter” and went on to say that tax reform was a way to “continue this growth” and “reinvigorate America’s economy.”

On Friday, Mr. Hassett and the Council of Economic Advisers released projections of how one prospective provision of the tax plan — a reduction in corporate tax rates to 20 percent from 35 percent — would affect economic growth. They said it would expand output by 3 to 5 percent over the long run, a period left unspecified.

The complication is that faster growth could undermine the party’s case that tax cuts are needed to add fuel to an economy that is already running with low unemployment — and it could lead the Federal Reserve to increase interest rates more quickly, which could dampen the effects of any tax bill.

Liberal economists said the report showed the success of Ms. Yellen at the Fed and undermined the case for the Republican tax bill. “The underlying trend in G.D.P. growth is clearly telling us two things,” Jared Bernstein, a former economic adviser to President Barack Obama who is now at the Center on Budget and Policy Priorities, said by email. “Keep on rockin’ steady with Yellen at the Fed, and there’s no need for a big, wasteful tax cut.”

The Fed, judging that the economy is growing about as fast as it can, is on course to raise its benchmark interest rate in December to a level Fed officials have described as likely neither to encourage nor to discourage growth. The Fed’s plans do not reflect the potential economic impact of a tax cut.

Aside from the details of the legislation, the Fed’s reaction may also depend on its leadership. Mr. Trump is expected to announce next week whom he will nominate to lead the Fed after Ms. Yellen’s term ends in early February.

The growth figure released on Friday was the government’s first estimate of economic output for the quarter, and it will be revised twice. Economists initially expected that Hurricanes Harvey and Irma would deal a blow to the country’s steady growth — a prospect reinforced by a net job loss in September — but became more optimistic in recent weeks.