The US ratings service Moody's lowered by one level its rating for four of the biggest US banks after a review that began in August, news reports said Thursday.
Morgan Stanley, Goldman Sachs Group, JPMorgan Chase & Co and Bank of New York Mellon had their senior holding company ratings lowered, dpa reported.
Moody's took the step after deciding the US government would be less likely to help them repay creditors in a crisis.
Under new rules being prepared by US banking regulators the government would step in and manage a bank in crisis without taxpayer assistance. The rules would require investors to accept losses and could require bonds to be converted into equity capital, according to Bloomberg news.
"We believe that US bank regulators have made substantive progress in establishing a credible framework to resolve a large, failing bank," Robert Young, a managing director at Moody's, said in a statement. "Rather than relying on public funds to bail out one of these institutions, we expect that bank holding company creditors will be bailed-in and thereby shoulder much of the burden to help recapitalize a failing bank."
The rules come as governments around the world attempt to avoid a repeat of the bailouts that occurred during the credit crisis years.
Moody's also affirmed the senior holding company ratings of Bank of America, Citigroup, State Street and Wells Fargo.