Chairman Ben S. Bernanke will probably reduce the Federal Reserve's monthly bond buying in the fourth quarter to $50 billion from $85 billion as he begins to unwind record stimulus, economists said in a Bloomberg survey.

Policy makers must find a way to slow the pace of purchases enough to signal confidence the economy is strengthening without prompting a sudden rise in interest rates, said former Fed economists Michael Feroli and Joseph LaVorgna. They said that probably means the Fed, which concludes a policy meeting today, will follow a three-step strategy to wind down bond buying.

“There is concern the first taper would be misinterpreted as the onset of a tightening cycle” and cause interest rates to go up, said Feroli, chief U.S. economist at JPMorgan Chase & Co. in New York. An initial reduction to $50 billion to $60 billion a month, followed by a second cut to $30 billion and then a halt to bond buying “would be enough of a runway to know and gauge the effects of what they're doing, but not too long a runway where it's a painfully interminable process.”