Fed Williams: QE3 asset purchases may be expanded

`` The Federal Reserve could expand its stimulus package to include assets other than mortgage-backed securities if the U.S. economy fails to respond to its latest effort to jump-start the economy. "Unlike our past asset-purchase programs, this one doesn't have a preset expiration date," said San Francisco Fed President John Williams at a speech at the City Club on Monday. "Instead, it is explicitly linked to what happens with the economy."''