Bernanke said in a statement to Congress that US economic growth continues at a moderate pace and, despite a slump in prices in the past two months that has sparked some fears of deflation, the Fed still sees inflation running at or below the the central bank's two percent target rate.
On the other hand, he pointed to continued weaknesses in the economy, especially high joblessness and the drag on growth of federal spending cuts.
"A premature tightening of monetary policy could lead interest rates to rise temporarily but would also carry a substantial risk of slowing or ending the economic recovery and causing inflation to fall further," Bernanke told Congress's Joint Economic Committee.
The Fed's policy board, the Federal Open Market Committee, he said, "is aware that a long period of low interest rates has costs and risks."
"Recognising the drawbacks of persistently low rates, the FOMC actively seeks economic conditions consistent with sustainably higher interest rates," he said.