Central bankers yesterday retained a pledge to keep their benchmark rate “exceptionally low” for an “extended period,” one year after first using the phrase. While the economy is improving, employers are still reluctant to hire, homebuilding is “depressed” and inflation will be “subdued for some time,” the Federal Open Market Committee said in a statement after meeting in Washington.

Chairman Ben S. Bernanke and his colleagues are waiting for sustained increases in employment before starting to exit a record expansion of credit, said Charles Lieberman, a former Fed official. Stocks and Treasuries extended gains as traders pared bets the central bank will raise rates over the next 12 months.

“It’s very difficult to make a strong case that the economy is in a self-sustaining recovery until we have job growth,”

said Lieberman, chief investment officer at Advisors Capital Management LLC in Hasbrouck Heights, New Jersey, and a former head of the monetary analysis staff at the New York Fed.

The FOMC left the federal funds rate target for overnight loans between banks in a range of zero to 0.25 percent, where it’s been since December 2008. Officials confirmed that their program to buy $1.43 trillion of mortgage-related debt will be completed by the end of March.