Aug. 8 (Bloomberg) -- Federal Reserve officials tomorrow 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."

The drop in global stocks, further fueled by concerns over Europe's debt crisis, adds to pressure on the Fed, which is confronting a slowing U.S. economy and unemployment stuck above 9 percent. Policy makers plan to hold a one-day meeting tomorrow and release a statement at around 2:15 p.m.

"The mounting worries threaten to tip an already fragile recovery into recession," said Julia Coronado, chief economist for North American for BNP Paribas in New York.

David Fuller's view These measures have been aired before but I think the Fed could do something more imaginative since rates on longer-term debt are not the problem.

Central bank and government responses to the current crisis reflected by plunging stock markets are discussed in the next item below.