NEW YORK, June 26 (Reuters) - The cost of protecting Citigroup's (C.N: Quote, Profile, Research) debt with credit default swaps rose on Thursday after Goldman Sachs said the largest U.S. bank may suffer $8.9 billion of second-quarter write-downs.

Citigroup's five-year credit default swaps rose to 135 basis points, or $135,000 a year to protect $10 million of debt, up 7 basis points from Wednesday's close, according to data from Phoenix Partners Group. For details click on [ID:nBNG32979]. (Reporting by Dena Aubin; Editing by Theodore d'Afflisio) (dena.aubin@thomsonreuters.com; +1-646-223-6325; Reuters Messaging: dena.aubin.reuters.com@reuters.net))