(Adds comments on inflation)

By Michael S. Derby

NEW YORK--A veteran central-bank official on Friday said the time may be coming when the Federal Reserve should start ramping down its purchases of Treasury and mortgage bonds.

"While our policies have been effective, our experience with our asset-purchase programs is limited and, as a result, we must analyze their benefits and costs carefully," Federal Reserve Bank of Cleveland President Sandra Pianalto said.

"Over time, the benefits of our asset purchases may be diminishing," the official said, as she pointed to a number of concerns she has with the program. While the nonvoting member of the Federal Open Market Committee said Fed bond buying and other stimulus have helped to get the economy back on its feet, there are a number of risks that, once considered, may call for changes in the pace of purchases.

"It is critical that we take these risks into consideration" as officials look to the future, Ms. Pianalto said.

"To minimize some of these risks, we could aim for a smaller-sized balance sheet than would otherwise occur if we were to maintain the current pace of asset purchases through the end of this year, as some financial market participants are expecting," the policy maker said. "This course of action would be all the more attractive if the economic outlook continues to improve, as I expect it will," Ms. Pianalto said.

The Fed is currently pressing forward with an open-ended program to buy bonds to boost growth and lower unemployment. While most expect these purchases to continue through much of the year, some central bankers have been arguing that it soon may be time to make the bond-buying program smaller as the economy's recovery picks up.

Ms. Pianalto's comments came from the text of speech she was giving in Bonita Springs, Florida.

In her speech, the official said that she expects the U.S. economy to grow by 2.5% this year and by 3% in 2014. That growth will bring only a slow retreat from what is now a 7.9% unemployment rate. Ms. Pianalto sees the jobless rate at 7.5% by year end and 7% by the close of 2014. She flagged the recovery in housing and said she expected to see a positive wealth effect that could lift consumer spending.

In comments given in response to audience questions, Ms. Pianalto said it remains critical that the Fed deliver on its mandate to keep prices stable. "Inflation has stayed low and stable, in fact, in 2012, we were concerned we would face a disinflation environment," she said. "It is important for the Federal Reserve to manage inflation expectations and to monitor them," the official said.

--Christopher Guinn contributed to this article

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