Credit flowing to American companies is drying up at a pace not seen in decades, threatening the creation of jobs and the expansion of businesses, while intensifying worries that the economy may be headed for recession.

The combined value of two leading sources of credit — outstanding commercial and industrial bank loans, and short-term loans known as commercial paper — peaked at about $3.3 trillion in August, according to data from the Federal Reserve. By mid-November, such credit was down to $3 trillion, a drop of nearly 9 percent.

Not once in the years since the Fed began tracking such numbers in 1973 has this artery of finance constricted so rapidly. Smaller declines preceded three recessions going back to 1975; at other times such declines tended to occur in conjunction with an economic downturn.

Policy makers at the Federal Reserve are growing increasingly alarmed about the problem, which is an outgrowth of the woes of the housing and mortgage industries. Just yesterday, the Fed’s vice chairman, Donald L. Kohn, said that the latest market turbulence appeared to be reducing credit to businesses and consumers, hinting that the central bank, in response, was prepared to cut interest rates further.