Standard & Poor's Corp. cut its ratings Tuesday on $32.1 billion of securities backed by alternative-A mortgages issued from 2005 through 2007, saying the bonds probably would not be able to cover projected losses due to higher delinquencies.

The rating agency downgraded 450 classes from 44 residential mortgage-backed deals and removed 305 of those ratings from watch for downgrading. S&P affirmed its ratings on another 177 classes from 39 of those deals.

It has been cutting ratings on billions of dollars of Alt-A and subprime residential mortgage-backed securities deals in recent months after a revision in the amount of losses expected. The change occurred as delinquencies continue to climb and home prices keep falling.

Subscribe Now

Access to authoritative analysis and perspective and our data-driven report series.

14-Day Free Trial

No credit card required. Complete access to articles, breaking news and industry data.