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Moody's has cut the credit ratings of big U.S. banks including Morgan Stanley, Goldman Sachs and JPMorgan Chase, after deciding that the federal government is less likely to bail the financial institutions out if they get into future difficulties. Goldman, Morgan Stanley and JPMorgan had the ratings on their long-term senior unsecured debt lowered one notch to Baa1, Baa2 and A3, respectively, Moody's said on Thursday. The credit ratings on the three banks' subordinated debt were also cut by one notch. The review by the second-largest rating agency, in terms of market share, follows a similar statement from rival Standard & Poor's in June, and comes as governments attempt to avoid a repeat of the bailouts of the credit crisis era. (Read more: Citadel's Ken Griffin: I would break up the big banks)

Wall Street reforms under the Dodd-Frank Act forbid the use of taxpayer money to save a failing bank and require the creation of a resolution authority to wind down institutions once they get into trouble, imposing losses on creditors in the process.

"We believe that U.S. bank regulators have made substantive progress in establishing a credible framework to resolve a large, failing bank," said Robert Young at Moody's. "Rather than relying on public funds to bailout one of these institutions, we expect that bank holding company creditors will be bailed-in and thereby shoulder much of the burden to help recapitalise a failing bank." (Read more: The problem with FedQE – Banks just aren't lending) The lower credit ratings could raise the cost of capital for the banks, many of which were already downgraded by Moody's following another major review undertaken last year.

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Regulators bicker over how to measure Dodd-Frank progress At the time, bank executives argued bitterly that the wide-ranging downgrades were unfair and that the agency was overcompensating for optimism before the financial crisis. This first review was designed to incorporate lessons from the crisis, when risks in banks' capital markets and trading businesses became evident. The agency warned at the time that it would re-evaluate its assumptions of US government support at a later date. "Dodd-Frank is intended to end tax payer-funded bailouts of banks that's the rationale for Moody's rating actions," said Peter Nerby, vice-president at Moody's.