Those measures could spur faster growth after a presidential campaign in which Mr. Trump regularly disparaged the economy’s performance under President Obama. But the Fed reiterated Wednesday that the economy is already expanding at roughly the maximum sustainable pace.

Fed officials also see evidence that the labor market is tightening. Several Fed districts reported labor shortages in the central bank’s most recent compilation of economic reports. In the Philadelphia district, construction workers are hard to find. Atlanta reported a shortage of nurses; Kansas City, truck drivers; Dallas, tech workers.

Faster growth, in the Fed’s judgment, would probably lead to higher inflation. As a result, if Republicans succeed in invigorating growth, the Fed is likely to raise rates more quickly. The greater the stimulus, the faster interest rates are likely to rise.

“Your expectation should depend very little on what you think that the F.O.M.C. is thinking and very much on your view of Trump policies and their macro effects,” said Jon Faust, a professor of economics at Johns Hopkins University and a former adviser to Ms. Yellen, referring to the Federal Open Market Committee. “Don’t focus on the Fed. As James Carville regularly reminded the other Clinton on the campaign trail: It’s the economy, stupid.”

Ms. Yellen emphasized that the Fed was not prejudging the likely course of events. She declined several times to comment on the merits of Mr. Trump’s plans or to predict their consequences for the economy.

“We’re operating under a cloud of uncertainty at the moment,” Ms. Yellen said.

Fed officials predicted that they would raise the Fed’s benchmark rate a little more quickly in the coming years, reaching 2.1 percent by the end of 2018. In September, they had predicted that it would reach 1.9 percent by the end of 2018. The new projections, however, reflect a significantly slower pace of increase than last December, when they expected the rate to reach 3.3 percent by 2018.