Standard & Poor's Corp. cut its ratings Monday on $11.28 billion of securities transactions backed by alternative-A mortgages issued from 2005 through 2007 and $1.35 billion of prime jumbo mortgage-backed securities issued in 2006, because of an increase in projected losses.

The rating agency lowered ratings on 385 classes from 13 alt-A transactions while affirming ratings on another 56 classes. More than 175 of the ratings had carried the top triple-A rating.

A separate S&P warning Monday affects ratings on 48 classes from three prime jumbo transactions issued in 2006.

S&P recently reported that delinquencies of home-related loans continued to climb in January, with the rate topping 20% for alt-A loans made in the past several years. Such mortgages, which sit between prime and subprime, often were granted without the borrower showing proof of income or assets, or both.

As a result of the ever-increasing delinquencies and expectations for more gains, S&P said it would nearly double its five-month-old projections on weighted average losses for alt-A loans from 2005 through 2007. Each successive year is seen performing worse than the last, with 2007 losses hitting 21%.

In the past few months, S&P has also cut its ratings on billions of dollars of bonds backed by mortgages issued to prime borrowers for high-priced homes, a segment were delinquencies have risen sharply.

S&P said it is assuming a loss severity of 40% on prime jumbo transactions issued in 2006 and 2007, because of falling home prices and the weakness of the housing markets. S&P removed 47 of the lowered ratings from watch for a possible downgrade.

S&P also affirmed its ratings on two classes of mortgage-backed securities and removed them from watch for a possible downgrade.

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