The Fed, Bernanke said, had counted on an expanding job market to “support moderate growth” in consumer spending. But the government reported Friday that hiring had fallen almost to zero in December and the unemployment rate had jumped to 5 percent from 4.7 percent — a rare one-month surge that almost always indicates coming hard times.

“It would be a mistake to read too much into any one report,” Bernanke said of the jobs report. “However, should the labour market deteriorate, the risks to consumer spending would rise.”

Bernanke said the Fed had successfully pumped money to banks and other lenders damaged in the mortgage crisis. Lending to banks directly from the Fed’s discount window, he said, had not worked as well as auctioning fixed multibillion-dollar sums.

Among other advantages, he explained, the auctions gave the Fed greater control over how much money was entering the financial system and the effect on interest rates. The auctions, he said, “may thus become a useful permanent addition to the Fed’s toolbox.”

“However much the Fed cuts rates between now and the spring,” said Brian Bethune, an economist at Global Insights, “the die is cast for a pretty rough six months and a very high risk of recession.”

Asked about the possibility of a recession, Bernanke sidestepped the question. As a Princeton University economist before he came to Washington, he said, he had served on a committee charged with setting the official starting and ending dates of each recession.

“You really cannot make a determination,” he said with a sly grin, “until well after the event.”