Federal Reserve Chairman Ben S. Bernanke tomorrow may disappoint stock investors betting on a commitment to step up stimulus. He has little choice, given rising consumer prices and a U.S. economy that is still growing.

Gasoline costs are 33 percent higher, consumer inflation is twice as fast and inflation expectations are above levels since Bernanke signaled more easing a year ago at the annual Fed symposium in Jackson Hole, Wyoming. While the U.S. expansion has slowed, the Chicago Fed's index of 85 economic indicators improved in July for a third month on gains in production.

Policy makers, who said Aug. 9 they'll use additional tools “as appropriate,” probably don't expect a recession or rapid disinflation, making a signal of bond buying premature, said Roberto Perli, managing director at International Strategy & Investment Group in Washington. Instead, Bernanke will probably detail options for further stimulus and clarify how much the Fed's reduction in its outlook this month stems from long-term obstacles to growth, said Keith Hembre, a former Fed researcher.