The Federal Reserve's latest drive to push down borrowing costs was necessary to support a frail economic recovery, Cleveland Fed President Sandra Pianalto said on Thursday.

The Fed's decision last month to pump an additional $600 billion into the economy through increased Treasury bond purchases has proven controversial, raising fears among some economists and politicians about a future spike in inflation.

But Pianalto argued that, while the measure is not a panacea, it should help the economy along and prevent an undesirable further decline in inflation, which many Fed officials already consider to be too low.

Our policy action offers the right kind of insurance that the Federal Reserve's monetary policy will support the economic expansion while stabilizing inflation and inflation expectations consistent with our price stability mandate, Pianalto said at an event hosted by Oberlin College.

She said an outright and potentially damaging decline in prices, known as deflation, was not likely. But she argued that such a trend would be harder to fight than inflation, making it crucial for the Fed to create a buffer against that risk.

Pianalto added that the Fed would regularly review incoming data on the economy and financial markets as it looks to adjust its level of policy easing, but gave no particular indication that she saw room for stopping purchases short of the $600 billion commitment.

Wading in on the debate over the nature of unemployment, she downplayed the notion of that a mismatch between available jobs and workers' skills was a primary reason for the country's elevated 9.6 percent jobless rate.

A group of economists at my bank have studied this question as well, and they conclude that most of the rise in unemployment our country has experienced is cyclical, not structural, she said.

A Labor Department report due out on Friday is expected to show a second straight month of employment gains. A Reuters poll shows analysts, on average, expecting a gain of 140,000 jobs, but no change in the unemployment rate.