Ongoing residential mortgage losses on loans written primarily in the 2005 through 2008 period performed weakly in the first quarter, Standard & Poor's Ratings Services said in a report Monday. Analysts for Standard & Poor's said GSE operating performance is more likely to worsen before it improves. Right now, the agency is rating Fannie Mae and Freddie Mac's senior debt as triple-A negative. "We expect Fannie and Freddie to keep requiring funds to pay the rising dividend they owe to the U.S. Treasury under its senior preferred stock purchase agreement," said Standard & Poor's credit analyst Daniel Teclaw. Fannie and Freddie did experience some decline in total mortgage delinquencies during the first quarter of 2011, but that positive development was offset by continued losses from seriously delinquent loans and foreclosures in certain segments of the GSE portfolios. S&P also blames weak GDP growth in April and May and high unemployment for stressing the GSEs along with the entire housing finance market. Write to Kerri Panchuk.