NEW YORK (Reuters) - Bond insurer MBIA Inc (MBI.N: Quote, Profile, Research) said on Wednesday that its losses from residential mortgages were well below estimates from Moody's Investors Service.

Moody's on Tuesday raised its forecast for losses from second-lien mortgages extended to subprime borrowers in 2006 and 2007. Based on the possibility of greater losses, the company warned that capital levels at bond insurers, including MBIA, could suffer.

"While it is unclear what impact, if any, the revised assumptions may have on MBIA, we believe that there are significant differences between subprime second-lien pools referenced in Moody's report and the prime second-lien securitizations we have guaranteed," MBIA said.

The company said Moody's had found that losses to date from subprime second-liens averaged 13.8 percent for 2006 and 7.1 percent for 2007.

By comparison, MBIA said that while some deals could see losses of more than 40 percent, the weighted average of cumulative losses on its second-lien loans was about 3.5 percent.

"We are comfortable with the resulting loss reserves and stress analysis we reported to the market," MBIA said.

Loans with lower credit scores and limited income documentation drove most losses at MBIA, but the insurer said these borrowers represented a small part of the collateral in its deals.

Moody's Investors Service is a unit of Moody's Corp (MCO.N: Quote, Profile, Research).

(Reporting by Joseph A. Giannone; Editing by Lisa Von Ahn)