Mr. Powell tried to emphasize that the Fed would continue to keep a close eye on economic conditions and said that the ultimate pace of rate increases was “not predetermined.” He has said the Fed’s goal is to strike a balance between extending the expansion and maintaining control of inflation.

But the overall tone of the statement suggested the Fed continues to regard the strength of economic growth as more impressive than any storm clouds on the horizon, including a trade war with China and geopolitical strains overseas. Companies continue to add jobs, the unemployment rate sits at 3.7 percent and wages are rising more quickly.

“Over the past year, the economy has been growing at a strong pace, the unemployment rate has been near record lows and inflation has been low and stable,” Mr. Powell said. “All of those things remain true today.”

Still, Mr. Powell noted that the robust expansion of 2018 would most likely moderate next year, and critics continued to raise questions about the Fed’s steady march toward higher rates. It now appears likely that inflation will fall short of the Fed’s 2 percent annual target for the seventh consecutive year. And Fed officials predicted on Wednesday that the central bank will miss the 2 percent target next year, too.

Low inflation is a sign of economic weakness and can be a problem in its own right, for instance by restricting the Fed’s ability to reduce borrowing costs should the economy begin to falter.

“I think they will look back on this as a mistake,” Josh Bivens, the director of research at the left-leaning Economic Policy Institute, said of the rate increase. “This threatens to snuff out the very beginning of wage gains that we’ve started to see recently in the data. The Fed should allow the expansion’s gains to reach more broadly into the work force and get off the steady escalator of ever-higher interest rates.”

Investors and some economists are increasingly concerned about the economic outlook, particularly as the sugar high from Mr. Trump’s $1.5 trillion tax cut and spending increases wears off and as the president continues to press trade fights with most of the nation’s major trading partners.