NEW YORK (Bloomberg) — Standard & Poor's raised its projection for losses on US sub-prime residential mortgage- backed securities issued in 2007 to 23 percent from 17.3 percent amid a worsening housing market.

Transactions from last year will have cumulative losses ranging from 21 percent to 25 percent, S&P said in a statement today.

The credit-ratings company will use the midpoint of those estimates to assess ratings on the debt. A loss projection of 19 percent for 2006 securities remains unchanged.

Loss projections are one of the factors used by S&P to assess whether to downgrade mortgage bonds.

S&P has reduced ratings on 6,414 asset-backed securities this year, according to Bloomberg data. The company said April 16 that it may downgrade $50.9 billion of structured finance securities based on residential mortgage-backed securities.

"If the growth in foreclosures continues unabated, additional adjustments to our lifetime loss estimates may be warranted," said analysts led by Andrew Giudici in the statement. Giudici said April 16 that S&P may raise its loss expectations.

Fitch Ratings, the third-biggest bond rating service, raised its loss expectations to 28 percent on March 20 and Moody's Investors Service projects losses at 19 percent.