NEW YORK - The U.S. commercial paper market expanded for a fourth straight week for the first time since December, adding to signs of an economic rebound as the global financial crisis continued to abate, Federal Reserve data showed on Thursday.

For the week ended Sept. 9, the size of the U.S. commercial paper market, a vital source of short-term funding for daily operations at many companies, rose by $11.3 billion to $1.174 trillion outstanding, up from $1.162 trillion the previous week.

Asset-backed commercial paper outstanding rose for the third consecutive week, up by $6.2 billion after rising by $19.5 billion the previous week.

Unsecured financial issuance outstanding rose by $6.2 billion after falling by $11.3 billion the previous week. (Reporting by John Parry; Editing by James Dalgleish)