WASHINGTON — Federal Reserve policymakers worried at their December meeting about the potential for a vicious cycle to develop in which credit problems could worsen. That could hurt economic growth and force the Fed to act more aggressively in cutting rates, according to meeting minutes made public Wednesday.

“Some members noted the risk of an unfavorable feedback loop in which credit market conditions restrained economic growth further, leading to additional tightening of credit,” the minutes said. “Such an adverse development could require substantial further easing” of rates, the minutes revealed.

Problems in the housing, credit and financial markets drove the Fed to do an about-face on Dec. 11 and slice its key interest rate yet again in the hope it would bolster an economy that was losing speed.

Fed Chairman Ben Bernanke and all but one of his colleagues agreed to trim the Fed key rate by one-quarter percentage point to 4.25 percent, a two-year low. The central bank ordered its key rate lowered three times last year; the December reduction was most recent one.

The decision to cut rates essentially marked a reversal for the central bank, which had hinted at its October meeting that the Fed’s two rate cuts probably would be enough to help the economy survive the housing and credit stresses. But the economy’s problems intensified after that meeting, forcing the Fed to change its stance.

“Members judged that the softening in the outlook for economic growth warranted an easing of the stance of policy at this meeting ... In view of the further tightening of credit and deterioration of financial market conditions, the stance of monetary policy now appeared to be somewhat restrictive,” the minutes said.

On Wall Street, stocks tumbled as oil prices briefly hit $100 a barrel and a weak report on manufacturing rattled investors. The Dow Jones industrials sank by 220.86 points to close at 13,043.96.

The 9-1 decision for a quarter-point reduction in December was opposed by Eric Rosengren, president of the Federal Reserve Bank of Boston, who preferred a bolder, half-percentage point cut. Wall Street, disappointed by the quarter-point cut, took a nosedive Dec. 11. The Dow Jones plunged more than 290 points.

In Rosengren’s view, the worsening housing slump, high energy prices and more cautious spending by individuals and businesses raised the risk of continued economic weakness, the minutes said. “In light of that possibility, a more decisive policy response was called for to minimize that risk,” the minutes said.

Fed policymakers were concerned that rising energy prices could spread inflation through the economy. That concern figured into the Fed’s decision to cut rates by a modest one-quarter point cut in December, the minutes suggested.

“Inflation pressures and risks remained,” according to the minutes.

To bolster the economy, many economists predict the Fed will slice rates yet again at its next meeting, on Jan. 29-30, the first regularly scheduled gathering of 2008.

“The Fed minutes are a testament that the economy is extremely volatile and policymakers have some very difficult decisions to make,” said Richard Yamarone, economist at Argus Research.

The economy is believed to have slowed sharply in the October-to-December quarter, probably to a pace of just 1.5 percent or less, according to analysts’ projections. Economic growth in the first three months of 2008 also is expected to be weak.

Economists’ big worry is that individuals will reduce spending and businesses will become reluctant to hire workers, throwing the economy into a tailspin. The odds of a recession have grown, with some economists putting it at just under 50 percent.

At the December meeting, Fed policymakers suggested all the housing, credit and financial problems have increased economic uncertainty. That has made it more difficult for the Fed to assess the country’s economic outlook and give clear signals about its next move.

“The committee agreed on the need to remain exceptionally alert to economic and financial developments and their effects on the outlook, and members would be prepared to adjust the stance of monetary policy if prospects for economic growth or inflation were to worsen,” the minutes said.

If economic conditions were to improve more rapidly than expected, “a reversal of some of the rate cuts might be appropriate,” according to the record of the meeting.

Although Fed policymakers agreed in December that rates must be cut yet again, “they also recognized that the situation was quite fluid and the economic outlook unusually uncertain,” the minutes said.

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