REFILE-Moody's changes Citigroup outlook to negative

(Corrects story link in third paragraph)

LONDON, April 18 (Reuters) - Moody's Investors Service on Friday affirmed Citigroup Inc's (C.N) ratings but changed the outlook to negative after investment bank charges came in higher than the ratings agency expected.

Moody's said it could downgrade Citigroup -- whose senior unsecured debt is rated Aa3, the fourth-highest investment-grade rating -- if the bank's capital ratios declined further due to continued losses.

Citigroup, the largest U.S. bank, on Friday posted its second straight quarterly loss, hurt by more than $16 billion in write-downs and increased reserves for credit losses. [ID:nNN1829842]

Moody's said it had affirmed the bank's ratings as its regulatory capital surplus remained sizeable despite the losses.

"Citigroup's capital position improved noticeably in the past seven months because the company has issued over $30 billion in regulatory capital," the agency said.

For Moody's full statement, please double click on [ID:nWLB0051] (Reporting by Richard Barley; Editing by David Holmes)