The Federal Reserve's total assets declined by 0.6 percent to $2.32 trillion during the past week as housing debt rolled off the balance sheet.
Total assets declined by $13.9 billion as of Wednesday, according to Thursday's weekly balance-sheet release. The Fed's holdings of mortgage-backed securities fell by $6.44 billion to $1.11 trillion. The Fed's holdings of federal agency securities declined by $2.17 billion to $157.2 billion.
The Fed said last week that as housing debt matures, it will purchase new Treasury securities to maintain its total securities holdings at $2.05 trillion.
The central bank bought $3.6 billion of Treasuries under the plan, which is aimed at preventing money from being drained out of the financial system, the Fed said today in a separate statement.
The purchases brought the total to $6.16 billion since policy makers began the program on Aug. 17, the first outright acquisition of U.S. debt by the Fed since October.