The Fed "can certainly have a meaningful contribution to supporting recovery, but in the worst case scenario where the economy goes off the broad fiscal cliff, which according to CBO and to our own analysis, the Fed (doesn't have the) tools to offset that," he said. "So it's important for congress to address the fiscal issues soon."

Though Bernanke delivered no assurances Tuesday, consensus is that ultimately the Fed will continue to buy about $40 billion worth of mortgage-backed securities per month and halt its Operation Twist program at the end of the year.

The Twist program entails selling shorter-dated securities and buying those on the far end of the curve in an effort to drive down long-term interest rates. However, the Fed is running out of short-dated notes and bills to sell.

In its place is likely to come a renewed effort to buy about $45 billion a month in Treasurys and continue to expand the Fed's $2.9 trillion balance sheet.

The combination of MBS and Treasurys purchases then would continue on an open-ended basis until the Fed reaches economic growth that would foster an acceptable level of unemployment, currently at 7.9 percent. (Read More: Sandy's Impact on Job Growth Will Be 'Acute': LaVorgna)

"Given the headwinds facing the US economy, including problems relating to US fiscal policy, it is hard to imagine a sustained acceleration in growth before the middle of 2013," economists at Nomura Securities said in an analysis. "That means that MBS purchases will likely go on until the third quarter of 2013."

Bernanke touted the benefits of the Fed's policy efforts.

"More generally, research suggests that our previous asset purchases have eased overall financial conditions and provided meaningful support to the economic recovery in recent years," he said.

The Fed likely will keep its promise to keep interest rates near zero until 2015.

"If there is any lesson from the financial crisis, it's that financial stability is paramount in meeting broader policy objectives," said Neal Soss, economist at Credit Suisse. "Raising rates too much or too soon could expose a key vulnerability in the financial system. This is yet another argument for expecting interest rates to remain at very low levels for a very long time".

Though stopping short of outlining exactly what future efforts would entail, Bernanke said the Fed stands at the ready to do what is necessary.

"We will want to be sure that the recovery is established before we begin to normalize policy," he said. "We hope that such assurances will reduce uncertainty and increase confidence among households and businesses, thereby providing additional support for economic growth and job creation."

Some investors, though, worry that the stimulative measures, known as quantitative easing, will exact a steep price in the future. The first two rounds helped boost the stock market and commodities, though the third round announced in September has had little effect.