WASHINGTON — The Federal Reserve chairman, Ben Bernanke, pledged today to slash interest rates yet again to prevent housing and credit problems from plunging the country into a recession.

The Fed chief made clear the central bank was prepared to act aggressively to rescue a weakening economy. “We stand ready to take substantive additional action as needed to support growth and to provide adequate insurance against downside risks,” he said.

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Some economists believe the Fed will slice its key interest rate by a bold half percentage point when the Fed meets next on January 29 and 30. Others, however, think the Fed will go with a more modest one-quarter percentage point reduction, given concerns that high energy prices could spark inflation.

To bolster the economy, the Fed lowered its key rate three times last year. Its last cut on December 11 left the rate at 4.25%, a two-year low. Still, Mr. Bernanke has come under criticism for not acting more aggressively to deal with the economy’s problems.

Worries about the country’s economic health have gripped voters, galvanized presidential candidates and spurred the White House and Congress to explore ways to stimulate the economy to avoid a recession.

Hiring practically ground to a halt in December, pushing the unemployment rate up to 5%, a two-year high, the government said in a report last week that rattled Wall Street and Main Street.

Mr. Bernanke, in a speech to a housing and economic forum here, cautioned against reading too much into one report. However, he said that if employment conditions were to continue to deteriorate, that would raise risks to the economy. The big worry is that consumers might cut back on their spending, sending the economy into a tailspin.

Incoming information suggests that the outlook for economic activity for this year has worsened and that the “downside risks to growth have become more pronounced,” Mr. Bernanke warned.

A housing slump, weaker home values, harder-to-get credit and high energy prices all “seem likely to weigh on consumer spending as we move into 2008,” Mr. Bernanke said.

Many analysts predict upcoming reports will show the economy grew at a feeble pace of just 1.5% or less in the final three months of last year and will be weak in the first three months of this year as consumers — major shapers of overall economic activity — tighten their belts.

In light of such risks to the economy’s growth, “additional policy easing may well be necessary,” Mr. Bernanke said.

Galloping energy prices — oil recently surged past $100 a barrel before easing — can put a damper on economic growth and can also spread inflation through the economy if they force companies to boost the prices of many goods and services.

Mr. Bernanke acknowledged the situation could complicate the Fed’s job of trying to keep the economy growing, while making sure that inflation is under control.

So far, he said, people and companies have “reasonably well-anchored” expectations about where they think inflation will head in the months ahead, Mr. Bernanke said. “However, any tendency of inflation expectations to become unmoored or for the Fed’s inflation-fighting credibility to be eroded could greatly complicate” the Fed’s task of maintaining stable prices, he said.