Mr. Bernanke was referring to the Fed's unprecedented decisions last year to step in and financially back JPMorgan Chase & Co.'s takeover of then-troubled investment house Bear Stearns and throw its first of four financial lifelines to insurance giant American International Group.
In remarks at a Fed conference in Charlotte, N.C., Mr. Bernanke said the central bank was forced to act because the collapse of those companies would have dealt a serious blow to the financial system and the economy.
The situation underscores the need for new powers to allow the government to safely wind down such huge firms, he said. Mr. Bernanke and Treasury Secretary Timothy Geithner recently asked Congress for such powers.
Since the financial crisis erupted in 2007, the Fed's balance sheet -- its assets and liabilities -- has more than doubled to $2 trillion from $870 billion. Credit provided under the bailouts accounts for only 5 percent of that, Mr. Bernanke said.
"These operations have been extremely uncomfortable for the Federal Reserve to undertake and were carried out only because no reasonable alternative was available," he said.
He signaled that the central bank is keeping a close eye on commercial banks' reserve balances held at the Fed. If those balances aren't managed right, they could complicate the Fed's task of "raising short-term interest rates when the economy begins to recover or if inflation expectations were to begin to move higher," Mr. Bernanke said.