Chairman Ben S. Bernanke moved the Federal Reserve further into uncharted policy territory in combating joblessness by tying the bank's interest-rate outlook to unemployment and inflation, while committing to an even faster expansion of the central bank's balance sheet.

The actions on the eve of the Fed's centenary year underscore Bernanke's hallmark commitment to experimentation and forceful action, derived in part from his research showing too little monetary stimulus produced large economic costs for the U.S. in the 1930s and for Japan in the 1990s. He called the current state of the labor market, with unemployment at 7.7 percent, "an enormous waste of human and economic potential" and said the benefits of more bond buying outweigh the potential risks.

"Bernanke is pulling out all the stops to kick this economy back into a higher gear," said Chris Rupkey, chief financial economist at Bank of Tokyo-Mitsubishi UFJ Ltd. in New York. "They are buying everything in sight — Treasuries, mortgage-backed securities — and will keep rates low until everyone who wants a job has one."