The Federal Reserve will probably decide today to expand Operation Twist beyond $400 billion to spur growth and buy protection against a deeper crisis in Europe, according to a Bloomberg News survey of economists.

Fifty-eight percent of respondents in a June 18 poll said the Fed will prolong the program, which seeks to lower borrowing costs by extending the average maturity of the securities in the central bank's portfolio. The current program ends this month.

Policy makers led by Chairman Ben S. Bernanke may conclude that growth is too feeble to reduce unemployment much further after payroll growth came close to stalling in May. At the same time, with inflation close to their 2 percent goal and the Greek election reducing the risk of a euro breakup, they may decide an additional round of quantitative easing isn't needed for now, economists said.