NEW YORK (AP) ― Moody’s Investors Service said Thursday that it has put the debt ratings of six of the largest U.S. banks on review due to changing federal policies for supporting distressed banks.

The rating agency said in March that it would review its assumptions of how much support banks can expect to receive from the U.S. government if they hit hard times. Regulators are working with large U.S. banks to develop liquidation plans in case of another financial crisis. But Moody’s believes that level of support could be lower and that the FDIC may not have enough reach under its authority to fully support the interconnected banking systems.

Moody’s put the debt ratings of four banks on review for downgrade: Goldman Sachs Group Inc., JPMorgan Chase & Co., Morgan Stanley and Wells Fargo & Co. It said that two ― Bank of America Corp. and Citigroup Inc. ― are on review but with an uncertain direction. Included in the review are the short-term ratings of several related bank holding companies.