The Federal Reserve is torn over when to slow its aggressive efforts to stimulate the economy.
Stock prices gyrated through the day as investors struggled to determine whether the Fed might soon pull back -- even gradually -- on its extraordinary efforts.
The Fed is buying bonds to try to ease long-term borrowing costs, encourage borrowing and accelerate growth. And it has said it will maintain its pace of bond purchases until the job market improves substantially.
Economists don't expect the Fed to curtail the bond purchases next month. But Paul Ashworth, chief U.S. economist for Capital Economics, said change at the September meeting is a real possibility.
For one thing, Bernanke told lawmakers Wednesday that the Fed might reduce the purchases within the next few meetings if the job market showed "real and sustainable progress." Bernanke is scheduled to hold a news conference after the September meeting, so Ashworth said it would allow him to directly explain the change then.
Still, whatever the Fed does is likely to be done gradually, Ashworth said.
"It could begin with a relatively trivial reduction to gauge market reaction," he said.
Most of Bernanke's testimony Wednesday to the Joint Economic Committee focused on the many risks the U.S. economy still faces and the help the Fed's support programs have provided.
His remarks suggested that the Fed isn't ready to taper the bond purchases.
In recent weeks, the job market and the broader economy have shown renewed vigor. The U.S. unemployment rate has reached a four-year low of 7.5 percent.
A resurgent national housing market has helped lift consumer confidence. And a powerful stock market rally has made many consumers feel wealthier.
Unemployment remains well above levels consistent with healthy economies. And some economic sectors like manufacturing are struggling. Bernanke also said higher taxes and deep federal spending cuts will likely slow growth this year.