Mr. Powell did not directly address how long the Fed planned to remain patient but suggested any future rate increases would depend largely on signs of inflation, which has consistently fallen below the Fed’s 2 percent target.

“I would want to see a need for further rate increases, and for me a big part of that would be inflation,” he said.

Brian Coulton, chief economist at Fitch Ratings, said he expected economic growth to continue and therefore he expected the Fed to resume rate increases this year. “This reads more like a pause than a strong signal that they believe that they are the end of the hiking cycle,” Mr. Coulton said. “Barring a very significant global downturn, we still see further rate increases later this year.”

Others, however, said the Fed may well have raised rates for the last time during the current economic expansion. “It does feel like the top of the cycle,” said Tim Duy, an economist at the University of Oregon who follows the central bank closely. “With the economy poised to slow over the next year, the Fed is not interested in risking turning that slowdown into a recession.”

The shift left some Fed watchers puzzling over why the central bank had reversed course so quickly.

In early October, Mr. Powell described the Fed’s benchmark interest rate as “a long way from neutral.” The comment was read by markets as implying that the Fed planned to continue raising rates for some time.

Mr. Powell sought to soften that impression in subsequent public appearances. After the Fed raised the benchmark rate by a quarter point at its December meeting, Mr. Powell said that the rate was at the lower end of what Fed officials consider the neutral zone: the region in which rates would neither stimulate nor restrain the economy. That implied the Fed was closer to pausing.

But Mr. Powell still said the Fed expected to keep raising its benchmark interest rate. And the Fed released projections showing most of its officials predicted at least two rate increases in 2019.