Federal Reserve officials left the door open to boosting their emergency programs to aid financial markets and the U.S. economy even as the worst recession in five decades shows signs of waning. The Fed’s Open Market Committee voted unanimously yesterday to keep unchanged its targets for purchases of long-term Treasuries and housing debt announced last month. At the same time, the panel will “continue to evaluate the timing and overall amounts” the central bank buys. The Fed said it will keep purchasing as much as $1.25 trillion of mortgage-backed securities, $200 billion of federal agency debt and $300 billion of Treasuries as part of efforts to reduce home-loan rates and “improve overall conditions in private credit markets.”