NEW YORK, April 21 (Reuters) - Fitch on Monday revised its ratings outlook to "negative" on some U.S. commercial mortgage-backed securities deals tied to General Growth Properties (GGWPQ.PK: Quote, Profile, Research), saying CMBS holders could be shortchanged as a result of the mall owner's bankruptcy filing.

The credit ratings agency revised its outlook from "stable" on 96 U.S. CMBS classes across the 20 transactions after the company and 158 of its properties, which are special purpose entities, filed for Chapter 11 bankruptcy protection.

Of the 158 properties, 63 properties secure 58 loans in Fitch-rated U.S. CMBS transactions.

Fitch said a bankruptcy court judge could prevent special servicers, who oversee delinquent mortgages in securitized pools, from foreclosing on the properties.

If the properties remain in bankruptcy, General Growth could seek to load up the properties with additional debt to help repay their corporate unsecured debt. These actions could cut into the cash flowing from the properties to the CMBS holders.

"The presence of additional debt would put substantial additional stress on the properties and impair the performance of the CMBS transactions," Fitch said.

At a minimum, CMBS trusts which include General Growth loans will incur additional servicing fees.

The company was forced to file for bankruptcy protection because it could not refinance its loans as they matured. However, most of loans that have not yet matured are performing and generate 1.78 times the cash flow needed to cover monthly debt payments.

Fitch is currently taking no additional actions on 20 other CMBS trusts with exposure to General Growth loans included in the bankruptcy filing. Of these, 10 CMBS deals have either an immaterial concentration of General Growth loans or have had prior rating actions taken because of the properties' deteriorating performances.