WASHINGTON (AP) — Federal Reserve chairman Ben Bernanke told Congress Wednesday the economic outlook remains "unusually uncertain," and the central bank is ready to take new steps to keep the recovery alive if the economy worsens.

Testifying before the Senate Banking Committee, Bernanke also said record low interest rates are still needed to bolster the US economy. He repeated a pledge to keep them there for an "extended period".

Bernanke downplayed the odds that the economy will slide back into a "double-dip" recession. But he acknowledged the economy is fragile.

Given that, the Fed is "prepared to take further policy actions as needed" to keep the recovery on track, he said. He didn't mention specific action being explored by the Fed policymakers. But they still have options beyond holding rates at record lows — including reviving some crisis-era programmes.

Bernanke is trying to send Congress, Wall Street and businesses a positive message that the recovery will last in the face of growing threats. At the same time, he wants to assure Americans that the Fed will take new stimulative actions if necessary.

Wall Street wasn't convinced. Shortly before Bernanke spoke, the Dow Jones industrial average was up about 20 points. Within minutes, stocks began falling and the Dow was down more than 120 points.

The recovery, which had been flashing signs of strengthening earlier this year, is losing momentum. And fears are growing that it could stall.