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Federal regulators say five of the biggest banks in the U.S. haven't worked out strong plans for how they might reshape themselves in case of failure, which could leave them unable to survive without another taxpayer bailout.

JPMorgan Chase, Bank of America, Wells Fargo, Bank of New York Mellon and State Street Bank were cited Wednesday by the Federal Reserve and the Federal Deposit Insurance Corp. for gaps in their bankruptcy plans known as "living wills" that they were required to submit. The five banks — with a total of about $5.6 trillion in assets — were among eight Wall Street behemoths whose plans were evaluated.

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The two agencies found the five banks' plans are "not credible" or insufficient for an orderly restructuring in the event of bankruptcy. The regulators gave the banks an Oct. 1 deadline to fix the problems or face possible "more stringent" requirements.

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"We are going to do everything we can to fix this issue," JPMorgan CEO Jamie Dimon said in a conference call with reporters.

In their 18-month review, the Fed and the FDIC also found weaknesses that must be addressed in the plans of Goldman Sachs and Morgan Stanley. The agencies' assessments differed. Only the FDIC deemed Goldman's plan "not credible," the more serious label, while only the Fed accorded the "not credible" finding to Morgan Stanley.

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The agencies also found shortcomings to be fixed in Citigroup's plan, but they didn't rise to the "not credible" level.

All eight banks must file the next round of plans by July 1 of next year.

The exercise was mandated under the financial overhaul law enacted in the wake of the crisis that struck in 2008 and set off the Great Recession. It is designed to check that big banks — which received hundreds of billions in bailouts — are prepared in case of financial disaster and aren't "too big to fail."