Mr. Powell said he hoped that the Fed could bring down inflation while preserving a strong labor market, which he said might lead the unemployment rate—near half-century lows of 3.6% in April—to rise slightly. “It may not be a perfect labor market,” he said.

The central bank is raising interest rates as part of its most aggressive effort in decades to curb upward price pressures. Mr. Powell signaled Tuesday that the central bank was likely to follow a half-percentage-point raise earlier this month, to a range between 0.75% and 1%, with similar moves at meetings in June and July. Until this month, the Fed hadn’t raised rates in such intervals since 2000.

The Fed last year maintained aggressive stimulus to spur a faster labor-market recovery. Mr. Powell said Tuesday that it was possible that disruptions from the pandemic had changed the labor market in ways that made current levels of unemployment inconsistent with the Fed’s 2% inflation goal.

He said that it seemed the unemployment rate consistent with stable inflation “is probably well above 3.6%.”

The Fed chairman repeated his hope that the central bank can curtail high inflation without spurring a large rise in unemployment. However, Mr. Powell said, there is little from modern economic experience to suggest that outcome can be achieved. “If you look in the history book and find it—no, you can’t,” he said. “I think we are in a world of firsts.”

Wells Fargo

& Co. Chief Executive

Charlie Scharf,

speaking at the same event Tuesday morning, said it would be difficult to avoid a recession but noted that consumers and businesses remain financially solid.

“The fact that everyone is so strong going into this should hopefully provide a cushion such that whatever recession there is, if there is one, is short and not all that deep,” he said.

Mr. Powell said he wasn’t at odds with those who believe the Fed faces a difficult path toward achieving what is known as a “soft landing,” in which growth slows enough to bring down inflation without triggering a recession.

“I would say there is no disagreement really. It is a challenging task, made more challenging the last couple months because of global events,” he said. “It is challenging because unemployment is very low already and because inflation is very high.”

Fed officials described higher inflation a year ago as temporary. They backed away from that characterization last fall, as the labor market healed rapidly and price pressures broadened.

Still, the Fed as recently as January had expected inflation to diminish this spring as supply-chain bottlenecks improved. Russia’s invasion of Ukraine in late February and rolling Covid-related lockdowns in China created new sources of inflationary pressure.

“That is going to make it harder for inflation to come down, so it has added a degree of difficulty to what was already a challenging market,” said Mr. Powell.

The Fed’s stopping point for rate increases isn’t certain. If inflation doesn’t show signs of diminishing soon, more officials could conclude that rates need to rise closer to 4% over the next 12 to 18 months, rather than to a level around 3% that most of them projected at their policy meeting two months ago.

“We will go until we feel like we are at a place where we can say, ‘Yes, financial conditions are at an appropriate place. We see inflation coming down,’” Mr. Powell said. “We will go to that point, and there will not be any hesitation about that.”

The most recent inflation data has been mixed. On a monthly basis, the consumer-price index’s gauge of core prices—which excludes food and energy—rose a seasonally adjusted 0.6% in April, according to a Labor Department report last week, and rose 6.2% over the previous 12 months.

The Fed uses a different gauge: the personal-consumption expenditures price index. April inflation data from that Commerce Department report will be released on May 27. Based on other recently released figures, Wall Street forecasters estimate a more muted rise in inflation using that measure.

Economists at

Morgan Stanley

think core PCE inflation rose by less than 0.3% in April, bringing the 12-month rate of change to 4.8%, from 5.2% in March.

“This is not a time for tremendously nuanced readings of inflation,” Mr. Powell said. “We need to see inflation coming down in a convincing way. Until we do, we’ll keep going.”

Write to Nick Timiraos at nick.timiraos@wsj.com and Michael S. Derby at michael.derby@wsj.com

Corrections & Amplifications
Federal Reserve Chairman Jerome Powell said, “Restoring price stability is an unconditional need.” An earlier version of this article incorrectly quoted him as saying it is a “non-negotiable need.” (Corrected on May 17,)