In his news conference, Bernanke noted that the Fed expects the economy's growth to remain only moderate over the next year. He pointed to the persistently depressed housing market and continued tight credit for many consumers and companies.
Julie Coronado, an economist at BNP Paribas, said she thought the Fed is signaling it will boost its purchases of bonds and other assets if the economy's growth fails to accelerate, even if it doesn't slow.
That is a "very low bar indeed," she wrote in a note to clients.
The Fed described inflation as "subdued." That was a more encouraging description than it offered last month. A more positive outlook on prices gives the Fed more room to keep rates low.
"This is a fairly clear-cut signal that inflation is not on their radar at this point," Tom Porcelli, an economist at RBC Capital Markets, wrote in a research note.
The Fed's statement was approved on a 9-1 vote. Jeffrey Lacker, president of the Richmond regional Fed bank, dissented. He objected to the new time frame for a rate increase.
The extended time frame is a shift from the Fed's previous plan to keep the rate low at least until mid-2013. Some economists said the new late-2014 target could lead to further Fed action to try to invigorate the economy.
The central bank has kept its key rate at a record low near zero for about three years. Its new time frame suggests the rate will stay there for roughly an additional three years.
Beyond the adjusted outlook for interest rates, Wednesday's statement closely tracked the Fed's previous comments about economic conditions. It used the same language as before in describing Europe's debt problems and the impact on the world economy.
The economy is looking a little better, according to recent private and government data. Companies are hiring more, the stock market is rising, factories are busy and more people are buying cars. Even the home market is showing slight gains after three dismal years
Still, the threat of a recession in Europe is likely to drag on the global economy. And another year of weak wage gains in the United States could force consumers to pull back on spending, which would slow growth.
The Fed has taken previous steps to strengthen the economy, including purchases of $2 trillion in government bonds and mortgage-backed securities to try to cut long-term rates and ease borrowing costs.
Some Fed officials have resisted further bond buying for fear it would raise the risk of high inflation later. And many doubt it would help much since Treasury yields are already near historic lows.
The Fed said Wednesday that it would keep its holdings of Treasury securities and mortgage-backed bonds at record levels and continue a program to further drive long-term rates lower by selling shorter-term securities and buying longer-term bonds.