WASHINGTON — To prevent inflation from taking off, the Federal Reserve will need to start boosting interest rates quickly and aggressively once the economy is back on firmer footing, Fed officials warned Tuesday.

WASHINGTON — To prevent inflation from taking off, the Federal Reserve will need to start boosting interest rates quickly and aggressively once the economy is back on firmer footing, Fed officials warned Tuesday.

"I expect that when it comes time to tighten monetary policy, my colleagues and I will move with an alacrity that, if needed, will be equal in speed and intensity" to when the Fed was slashing rates to battle the recession and the financial crisis, said Richard Fisher, president of the Federal Reserve Bank of Dallas.

Although Fisher has a reputation for being one of the Fed's toughest inflation fighters, it marked the second such warning by a central bank official in recent days. Fed member Kevin Warsh on Friday said the central bank will need to move swiftly when the time comes to raise rates.

Charles Plosser, president of the Federal Reserve Bank of Philadelphia and also a hawk against inflation, waded into the debate in a speech Tuesday in Easton, Pa., saying the Fed may need to act "well before" unemployment — now at a 26-year high of 9.7 percent — returns to normal. The Fed, he said, will need to be on guard "to prevent the Second Great Inflation."

It's all part of a high-wire act that the Fed has to perform as the economy transitions from recession to recovery.

If the Fed raises rates and reels in the unprecedented support too soon, it could short-circuit the rebound. If the central bank waits too long to rein in its stimulus, inflation could be unleashed.

"The wind-down process needs to begin as soon as there are convincing signs that economic growth is gaining traction and that the lending capacity of the banking system is capable of expansion," according to excerpts of a speech Fisher delivered in Dallas. That also was similar to Warsh's comments last week.

Some investors found Warsh's comments confusing, especially coming just two days after the Fed decided to hold its key bank lending rate at a record low near zero and pledged to keep it there for an "extended period." Most economists read that to mean the Fed would keep rates at super-low levels through this year and into part of 2010.

Warsh's comments led some investors to believe that rate increases could come sooner. The last time the Fed raised rates was in June 2006, around the time that the housing bubble reached its peak.