LONDON, May 14 (Reuters) - Moody's Investors Service on Wednesday cut the financial strength rating of U.S. mortgage provider Freddie Mac (FRE.N: Quote, Profile, Research) as it expects the company to rack up further credit losses.

Moody's cut Freddie Mac's bank financial strength rating to B+ from A- but affirmed its senior debt at Aaa, the highest rating.

Freddie Mac on Wednesday reported a net loss of $151 million and said it would raise $5.5 billion in capital.

"Moody's downgraded Freddie Mac's BFSR to B+ from A- because it expects Freddie Mac to incur substantial credit losses that will reduce its financial flexibility even after taking into account its planned capital issuance," the agency said in a statement.

It said the rating now incorporated cumulative credit losses in 2008 and 2009 of up to $7.5 billion. Moody's said it affirmed Freddie Mac's Aaa senior debt rating as the company benefits from "very high systemic support because of its central role in mortgage finance in the United States."

For Moody's full statement, please double click on [ID:nWLB1594]; for a story on Freddie Mac's results, please double click on [ID:nN14475514].

(Reporting by Richard Barley; editing by Rory Channing)