Federal Reserve Chairman Jerome Powell said Thursday that he and his fellow policymakers are encouraged by the slowing pace of inflation but are unsure whether they’ve done enough to keep the momentum going.

Speaking a little more than a week after the central bank voted to hold benchmark policy rates steady, Powell said in remarks for an International Monetary Fund audience in Washington, D.C., that more work could be ahead in the battle against high prices.

“The Federal Open Market Committee is committed to achieving a stance of monetary policy that is sufficiently restrictive to bring inflation down to 2 percent over time; we are not confident that we have achieved such a stance,” he said in his prepared speech.

For the second time in recent weeks, a public address from Powell was interrupted by climate protesters. He briefly left the stage before resuming.

The speech comes with inflation still well above the Fed’s long-standing goal but also considerably below its peak levels in the first half of 2022. In a series of 11 rate hikes that constituted the most aggressive policy tightening since the early 1980s, the committee took its benchmark rate from near zero to a target range of 5.25%-5.5%.

Those increases have coincided with the Fed’s preferred inflation gauge, the core personal consumption expenditures price index, to fall to an annual rate of 3.7%, from 5.3% in February 2022. The more widely followed consumer price index peaked above 9% in June of last year.

Powell said that inflation is “well above” where the Fed would like to see it while describing policy as “significantly restrictive.”

“My colleagues and I are gratified by this progress but expect that the process of getting inflation sustainably down to 2 percent has a long way to go,” he said. “We will keep at this until we succeed,” he later added, saying the Fed is focused on whether rates need to go higher and how long they need to stay elevated.

Stocks headed lower after the speech, with the Dow Jones Industrial Average down close to 200 points. Treasury yields lurched higher after declining for most of the past three weeks, propelled up in large part after a poorly received 30-year bond auction.

“Chairman Powell issued a warning to investors too giddy on the prospect of rate cuts next year,” said Jeffrey Roach, chief economist at LPL Financial. “The Fed will be true to its mandate and hike further should inflation reaccelerate.”

As he has in recent speeches, Powell stressed that the Fed nevertheless can be cautious as the risks between doing too much and too little have come into closer balance. He said the Fed is attuned to the rise in Treasury yields.

“If it becomes appropriate to tighten policy further, we will not hesitate to do so,” he said. “We will continue to move carefully, however, allowing us to address both the risk of being misled by a few good months of data, and the risk of overtightening.”

“Monetary policy is generally working the way we think it should work” Powell said during a discussion following his speech.

Markets are largely convinced the Fed is through hiking rates.

Futures pricing, according to the CME Group, indicates less than a 10% probability that the FOMC will approve a final rate hike at its Dec. 12-13 meeting, even though committee members in September penciled in an additional quarter percentage point rise before the end of the year.

Traders anticipate the Fed will start cutting next year, probably around June.

Powell noted the progress the economy has made. Gross domestic product accelerated at a “quite strong” 4.9% annualized pace in the third quarter, though Powell said the expectation is for growth to “moderate in coming quarters.” He described the economy as “just remarkable” in 2023 in the face of a broad consensus that a recession was inevitable.

Unemployment remains low, though the jobless rate has risen half a percentage point this year, a move commonly associated with recessions.

But Powell noted that the Fed is “attentive” that stronger-than-expected growth could undermine the fight against inflation and “warrant a response from monetary policy.”

He also pointed out that improvements in supply chains have helped ease inflation pressures, but “it is not clear how much more will be achieved by additional supply-side improvements. Going forward, it may be that a greater share of the progress in reducing inflation will have to come from tight monetary policy restraining the growth of aggregate demand.”

The remarks are part of a broader presentation he is giving to the Jacques Polak Annual Research Conference. One broad policy topic he addressed was the challenge posed by keeping rates anchored near zero, where they were before the inflation surge. Powell said it is “too soon” to say whether zero-rate challenges are “a thing of the past.”