NEW YORK, July 9 (Reuters) - U.S. primary dealers showed scant interest in borrowing the Federal Reserve's U.S. agency debt holding at an auction the U.S. central bank held on Thursday.

The New York Fed conducts an auction for the U.S. central bank at noon each business day where primary dealers -- firms that deal directly with the Fed -- can borrow U.S. Treasuries overnight from the U.S. central bank's holdings.

The New York Fed said two days ago it will begin on Thursday lending debt issued by mortgage agencies Fannie Mae (FNM.N: Quote, Profile, Research) (FNM.P: Quote, Profile, Research), Freddie Mac (FRE.N: Quote, Profile, Research) (FRE.P: Quote, Profile, Research) and the Federal Home Loan Bank System, in addition to Treasuries, in a bid to help dealers to raise short-term cash.

Primary dealers bid to borrow six issues of agency bonds from the Fed's System Open Market Account (SOMA). These agency issues were worth $120 million, compared with more than $12 billion in Treasuries they requested to borrow from the Fed.

The SOMA lending move coincides with the Fed's program to buy agency bonds and mortgage-backed securities with the goal to bring down mortgage rates and stimulate the economy.

There were some concerns the Fed's purchases of these investments would make certain agency issues scarce, making it harder to fund trades tied to this sector, analysts said.

"Given the light bidding, it suggests people are not having funding problems in the overnight market," said Rudy Narvas, a senior strategist at 4Cast Ltd. in New York.

The Fed has said it intends to buy $200 billion in agency debt and up to $1.25 billion in mortgage-backed bonds. (Reporting by Richard Leong; Editing by Padraic Cassidy)