“We are seeing an impact from our policies,” Eric S. Rosengren, the Federal Reserve Bank of Boston president, said in a recent interview. But “I think we’re pushing the interest-sensitive sector about as far as we’re going to be able to push it at this time.”

Fed officials backed away from talk of an early retreat from the current program of asset purchases — $85 billion a month in Treasury and mortgage-backed securities — after economic growth and inflation both rose more slowly than expected in the first quarter.

The Fed’s preferred inflation gauge rose 1.2 percent, below its 2 percent target. But that is as far as the pendulum has swung.

The Fed chairman, Ben S. Bernanke, and his allies point to increased sales of homes and autos and the rising stock market as evidence that the asset purchases are working. “After reviewing the efficacy and costs of this program, I have concluded that the efficacy has been as high or higher than I expected at the onset of the program and the costs the same or lower,” William C. Dudley, president of the Federal Reserve Bank of New York, said in a recent speech.

But there are several reasons officials remain reluctant to do more. The benefits of additional asset purchases appear modest, at best. The consequences of buying more bonds are uncertain. And officials are frustrated that their monetary policy is being forced to play a role that most economists and Fed officials say could be more easily and effectively performed by fiscal policy.