WASHINGTON -- The Federal Reserve announced today a radical plan to buy massive amounts of short-term debts in a dramatic effort to break through a credit clog that is imperiling the economy.

The Federal Reserve will buy "commercial paper," a short-term financing mechanism that many companies rely on to finance their day-to-day operations, such as purchasing supplies or making payrolls.

The $99.4 billion daily market for this crucial financing, which relies on investors rather than banks, has virtually dried up. This has made it increasingly difficult and expensive for companies to raise money to fund their operations. Commercial paper is a way of borrowing money for short periods, typically ranging from overnight to less than a week.

The unstable situation has left many companies vulnerable. The notion under the plan is for the government to provide a "backstop" that would give companies a new place to get cash, the Fed said. The action makes the Fed a source of credit for nonfinancial businesses in addition to commercial banks and investment firms.

The Fed said it is creating a new entity to buy three-month unsecured and asset-backed commercial paper directly from eligible companies.

"The commercial paper market has been under considerable strain in recent weeks as money market mutual funds and other investors" have become increasingly reluctant to buy commercial paper, especially longer-dated maturities.

The Treasury Department, which worked with the Fed on the program, said the action is "necessary to prevent substantial disruptions to the financial markets and the economy." The Treasury will provide money to the Federal Reserve Bank of New York to support the new program, the Fed said.

If a company's commercial paper is not backed by assets or other forms of security acceptable to the Fed, the company could pay an up-front fee, the central bank said.

The Fed said it hoped its effort would jolt the commercial paper market back to life.

"This facility should encourage investors to once again engage in term lending in the commercial paper market," the Fed said. That should eventually spur financial companies to lend to each other and to their customers, including consumers, the Fed said.