Federal Reserve Bank of Philadelphia President Patrick Harker said Thursday that while an interest rate rise lies some ways in the distance, he is ready for the U.S. central bank to begin slowing the pace of its asset buying stimulus this year.

“I am in the camp of starting the tapering process,” Mr. Harker said in an interview with The Wall Street Journal, referring to slowing the pace of the Fed’s $120 billion a month in bond purchases, which aim to augment the central bank’s near zero short-term interest rate target range.

Asked if the process should start this year, Mr. Harker said “yes,” adding that, “I would like to see tapering begin. I’d like to see it happen sooner rather than later. I’d like to see it being a slow, methodical process.”

Mr. Harker, who doesn’t currently have a vote on the rate setting Federal Open Market Committee, weighed in amid an active debate among central bank officials about paring support for the economy, which is roaring back to life from the impact of the coronavirus pandemic.

Officials have been focused on what to do with their $80 billion a month in Treasury bond buying and $40 billion a month in mortgage bond purchases. At the FOMC meeting last month, Fed Chairman Jerome Powell acknowledged officials are discussing pulling back on the support but offered no details for when, or how, that might play out.

A number of central bankers are on board with slowing the buying. During the interview, Mr. Harker said a large part of his case for trimming the stimulus comes down to the economy’s rebound. The main challenge now for the economy isn’t supporting demand, but sorting out supply to meet it, and in that regard the Fed’s asset buying doesn’t offer much help and could even come with risks for financial stability, he said.

A number of Fed officials have said they would in particular like to see the Fed trim its mortgage bond purchases because of the hot housing market. They argue that easing back on mortgage purchases would come with little negative consequence.

But Mr. Harker said the Fed should trim its purchases of Treasury and mortgage bonds equally. “If we start a tapering process, keep it simple,” he said.

“We’re talking about a process that once we start it, depending on how we do it, would be, say, 12 months in length,” Mr. Harker added. “We’re doing $120 billion a month, if we cut back $10 billion each month, we’d be done in 12 months, right? I think that’s a reasonable thing to do.”

Mr. Harker said he would like to see the process completed before the Fed raises interest rates. At the FOMC meeting, policy makers moved forward expectations of a rate rise and now see half a percentage points worth of increases in 2023, although a minority of policy makers favor raising rates next year.

“My forecast before was not touching the Fed funds rate until 2023. I’m still there right now,” Mr. Harker said.

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But what happens with inflation is key to that outlook, Mr. Harker said, noting he still believes the current inflation surge is tied to reopening issues and will abate by next year. If it doesn’t, it could weigh on his expectations for interest rate policy, he said.

“If we see inflation not behaving as we hoped, that is staying within our 2 percent-ish range, then I think we may have to act sooner” on interest rates, Mr. Harker said.

The Philadelphia Fed leader also said he believes the U.S. economy will grow by 7% this year and by about 3.5% next year, with the unemployment rate falling from 5.8% currently to 4.5% this year and to 3.8%, roughly full employment, by 2023. He said inflation should hit 3% to 3.2% this year and ease next year to the Fed’s 2% target.

Write to Michael S. Derby at michael.derby@wsj.com