U.S. Federal Reserve Chairman Ben Bernanke said Thursday that the recent credit crisis has created "significant market stress" and vowed the Fed will take steps to deal with the situation.

The market turbulence originated in concerns about subprime mortgages, but the resulting global financial losses "have far exceeded even the most pessimistic estimates of the credit losses on these loans." said Bernanke in prepared remarks for a congress hearing.

"Subprime mortgage losses that triggered uncertainty about structured products more generally have reverberated in broader financial markets, raising concern about the consequences for economic activity," Bernanke said.

"These wider losses reflect, in part, a significant increase in investor uncertainty centered on the difficulty of evaluating the risks for a wide range of structured securities products, which can be opaque or have complex payoffs," he warned. "Investors also may have become less willing to assume risk."

Bernanke promised the Congress that the Fed will make efforts to deal with the crisis.

"The Federal Reserve takes responsible lending and consumer protection very seriously," he said. "Along with other federal and state agencies, we are responding to the subprime problems on a number of fronts."

"We are committed to preventing problems from recurring, while still preserving responsible subprime lending," he added.

The Fed cut its base federal rate by 0.5 of a point to 4.75 Tuesday.

The action was intended to help forestall some of the adverse effects on the broader economy that might otherwise arise from the disruptions in financial markets and to promote moderate growth over time, explained Bernanke.

"Recent developments in financial markets have increased the uncertainty surrounding the economic outlook," he said, adding that the Fed "will continue to assess the effects of these and other developments on economic prospects and will act as needed to foster price stability and sustainable economic growth."