Federal Reserve Chairman Ben S. Bernanke says he'll stoke the economy until the job market recovers “substantially.” That promise may force him to keep buying bonds until the final months of his term ending in January 2014, according economists in a Bloomberg survey.

Sixty-eight percent of 60 economists said the Fed chairman's third round of quantitative easing will last until late next year or beyond. Just 51 percent of them said the strategy will help boost employment, with a median estimate of 116,000 jobs over the course of next year.

“The recovery in the labor market is probably going to be more sluggish than the Fed recognizes” said Michael Hanson, senior U.S. economist at Bank of America Corp. in New York and a former Fed economist. He said policy makers have “painted themselves in a bit of a corner, waiting to see a significant improvement in the labor market.”