Standard & Poor’s downgraded the credit ratings of J.P. Morgan Chase & Co., Goldman Sachs Group and six other major U.S. banks, saying it is no longer confident that the U.S. government would step in to support them in a future crisis.

S&P cut its ratings of the nonoperating holding companies (NOHC) of the eight U.S. banks determined to be “globally systemically important” by one notch. That has lowered ratings for Goldman Sachs GS, -2.87% , Citigroup Inc. C, -3.32% , Morgan Stanley MS, -2.54% and Bank of America Corp. BAC, -2.84% to BBB-plus, placing them just three notches above speculative, or “junk” status.

It cut J.P. Morgan to A-minus, and lowered State Street Corp. STT, -1.88% , Bank of New York Mellon Corp. BK, -0.68% and Wells Fargo & Co. WFC, -3.46% to A.

The move comes as the Federal Reserve works to complete rules that will dictate the amount and type of capital banks must hold to absorb a major shock to the financial system. The Fed said in October that the country’s six biggest banks are facing a $120 billion capital shortfall under rules that will require them to hold large amounts of debt that can be converted into equity in a crisis.

See:Fed approves rule to limit emergency loans

“Based on our review of progress made toward putting in place a viable U.S. resolution plan, we now consider the likelihood that the U.S. government would provide extraordinary support to its banking system to be ‘uncertain’ and are removing the uplift based on government support from our ratings,” S&P said in a statement.

The rules will set a minimum level of ‘total loss-absorbing capacity’ (TLAC) that banks must have to limit the impact that the failure of a single large institution could have on the entire financial system and avoid the kind of taxpayer bailouts that were needed — and controversial — during the 2008 financial crisis. The rules are part of the Dodd-Frank Act, the set of regulations put in place to address the issue of ‘too big to fail.”

Read: These are the world’s 30 ‘too-big-to-fail’ banks

The downgrade does not apply to the banks’ operating companies, as NOHC creditors could provide support to them, said S&P.

“These ratings now all include one notch of uplift from the implementation of our additional loss-absorbing capacity (ALAC) criteria,” said S&P.

The agency is keeping ratings on the core and highly strategic operating subsidiaries of Bank of America, Citi, Morgan Stanley and Goldman on CreditWatch positive, meaning it could upgrade them in the near term.

“We await sufficient clarity from regulators on which instruments will count toward total loss-absorbing capacity, which may result in an additional notch of uplift under our ALAC criteria for these banks,” said S&P.

S&P said it is uncertain whether legacy senior unsecured long-term debt instruments will be TLAC-eligible, although the Fed may be less stringent given the amount of debt banks may have to raise.

Read: New ‘too big to fail’ rules could force banks to raise up to $1.19 trillion