WASHINGTON  Taking a step to normalize lending after holding interest rates to extraordinary lows for more than a year to prop up the financial system, the Federal Reserve on Thursday raised the interest rate it charges on short-term loans to banks.

While the central bank had signaled its intentions to take such a step, the timing was a surprise. The announcement was made after the stock market had closed in a carefully worded statement that emphasized that the Fed was not yet ready to begin a broad tightening of credit that would affect businesses and consumers as they struggle to recover from the economic crisis.

But while the move will not directly affect home mortgage, credit card or auto loan rates, it was a clear sign to the markets, politicians in Washington and the country as a whole that the era of extraordinarily cheap money necessitated by the crisis was drawing gradually to a close.

The Fed’s board of governors raised the discount rate on loans made directly to banks by a quarter of a percentage point, to 0.75 percent from 0.50 percent, effective Friday.