By Howard Schneider and Ann Saphir

WASHINGTON (Reuters) -The Federal Reserve is "strongly committed" to fighting inflation, but there remains hope it can be done without the "very high social costs" involved in prior campaigns to control surging prices, Fed Chair Jerome Powell said on Thursday.

Powell, in a 40-minute webcast interview with Cato Institute President Peter Goettler, was not asked about the U.S. central bank's policy meeting later this month, when it is expected to raise its target interest rate by either half or three-quarters of a percentage point, and the Fed chief did not volunteer any information on his preference.

Investors in contracts tied to the Fed's policy rate currently anticipate the larger 75-basis-point increase, an expectation that rose through the day after the European Central Bank hiked its policy rate by three-quarters of a percentage point, and a decline in U.S. weekly jobless claims pointed to continuing strength in the labor market.

But Powell did restate what has now become the Fed's message of the moment: Policymakers won't back down on planned rate increases."We need to act now, forthrightly, strongly as we have been doing, and we need to keep at it until the job is done," Powell said. "The Fed has and accepts responsibility for price stability."

"My colleagues and I are strongly committed to this project and we will keep at it until the job is done."

The Fed will hold its next policy meeting on Sept. 20-21, when it will issue updated economic projections and almost certainly announce the fifth consecutive increase in the target federal funds rate. The release of a monthly U.S. consumer price inflation report next week will be the final major piece of data for policymakers to evaluate in making that decision.

Information since the Fed's July 26-27 meeting has given some small sense that the pace of inflation, which has been running at 40-year highs, may be slowing, but not enough for policymakers to feel confident it has peaked.