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S&P downgrades holding companies of eight U.S. banks

Customers are seen outside of a Bank of America in Tucson, Arizona January 21, 2011. REUTERS/Joshua Lott

(Reuters) - Standard & Poor's cut its nonoperating holding company (NOHC) ratings on eight U.S. "global systemically important banks" by one notch, citing uncertainty about the U.S. government's willingness to provide support to the banking system if it came under stress.

The ratings apply to the holding companies of Bank of America Corp (BAC.N), Citigroup Inc (C.N), Morgan Stanley (MS.N), Wells Fargo & Co (WFC.N), Bank of New York Mellon Corp (BK.N), State Street Corp (STT.N), JPMorgan Chase & Co (JPM.N) and Goldman Sachs Group Inc (GS.N).

The credit ratings on the banks' operating units are not affected by the downgrade.

The Federal Reserve said last week that big U.S. banks would have an extra year to calculate a capital requirement known as the supplementary leverage ratio for stress tests.

The supplementary leverage ratio creates hard limits on how much debt banks can borrow relative to their assets, without giving them credit for having relatively low-risk assets.

In October, the Fed also proposed a rule that would require six of the eight banks to raise an additional $120 billion to comply with a regulatory requirement.

The requirements are aimed at ensuring that the banks are able to recapitalize without disrupting markets or requiring a government bailout.

(Reporting by Sruthi Shankar in Bengaluru; Editing by Ted Kerr)