CNBC reports that JPMorgan Chase CEO Jamie Dimon has warned investors that the Fed could still be forced into a sharp policy move next year.

Fed Chairman Jerome Powell has already suggested that the central bank could start to dial back on its pandemic-era monetary stimulus before the end of this year. He is due to outline more details later on Wednesday at the end of the Fed’s two-day policy meeting.

Dimon said that if the U.S. continues to see inflation running hot over the next few months then the central bank could be forced to act quickly.

“If inflation is so high that the Fed has to do more traditional madmen economy, like jam on the brakes, pull out liquidity, then you’re going to see a huge reaction. And I’m not predicting that, but it’s possible they have to do that sometime next year,” Dimon said.

“The Fed can’t always be proactive — I mean, sometimes they’re going to have to be reactive.”

The top uncertainty for the Fed has been the path of inflation. The latest data showed U.S. consumer prices were up by 5.3% in the year to August, slightly down from the 13-year high of 5.4% in July.

Powell has argued that this spike in prices is transitory. But Dimon said that if those hot inflation figures continue into December then U.S. policymakers may have to admit that at least part of the price increases are here to stay.