Federal Reserve officials may move to bolster investor confidence after an unprecedented downgrade to America's credit rating and concern the U.S. may be headed for a recession sent global share prices tumbling.

Chairman Ben S. Bernanke and his colleagues may prolong a pledge to maintain record monetary stimulus, said economists at JPMorgan Chase & Co., BNP Paribas and Goldman Sachs Group Inc. The Fed could do so by making a commitment to hold its $2.87 trillion balance sheet steady for an "extended period." The Fed also may replace shorter-term securities with longer maturities to reduce rates on longer-term debt.

"Those steps are all about bolstering confidence," said Michael Feroli, chief U.S. economist at JPMorgan Chase in New York and a former Fed economist. "It wouldn't do tons to alter economic and financial conditions, but the perception that the Fed will act and do something is reassuring."