Speaking after the central bank announced yet more measures to stimulate the US economy, Bernanke said the situation in Europe was spilling over to the US.

He said he was hopeful European nations would do more to address the roiling crisis, which has called into question the future of the eurozone.

"We hope it does not get worse," Bernanke said with a nervous smile. "It is already one of the factors that has been a drag on the US economy."