Moody’s Investors Service cut its credit ratings on Bank of America, Citigroup and Wells Fargo on Wednesday, saying that Washington was now less likely to bail out the banks if needed.

“The downgrades result from a decrease in the probability that the U.S. government would support the bank, if needed,” Moody’s said.

The ratings agency said that it did think the government would provide some support to systemically important financial institutions. But the huge bailouts that rescued Bank of America and Citigroup and others during the financial crisis might not happen again, Moody’s said.

“It is also more likely now than during the financial crisis to allow a large bank to fail should it become financially troubled, as the risks of contagion become less acute.” the ratings agency said. It added that the moves “do not reflect a weakening of the intrinsic credit quality” of the bank.

The ratings agency cut Bank of America’s long-term senior debt to Baa1 from A2 and lowered short-term debt to Prime-2 from Prime-1.

Shares of Bank of America were down 3.7 percent in early afternoon trading.

In a statement, Bank of America said: “Moody’s decision to downgrade our credit rating is based on factors external to Bank of America: Their conclusion that the Dodd-Frank legislation will make the U.S. government less likely to support financial institutions in a crisis, and a possible further deterioration of the economy. In fact, Moody’s explicitly stated that the downgrades do not reflect a weakening of the intrinsic credit quality of Bank of America.”

The bank said it had made “significant progress” in improving its capital and liquidity positions.

During the financial crisis, Bank of America received some $45 billion in federal aid, which it has since repaid. The bank has been trying to shore up investor confidence as it continues to struggle with the legacy of tens of billions of dollars in bad mortgage assets. In recent weeks, it has announced an executive shakeup, a streamlining that will cut 30,000 jobs and a $5 billion investment by Warren E. Buffett.

Moody’s also cut its ratings on Citigroup’s short-term debt to Prime 2 from Prime 1, while affirming its A3 long-term rating.

Shares of Citigroup were slightly lower, at $26.85. In a statement, the bank said: “We completely disagree with Moody’s change to Citigroup’s short-term rating. It does not accurately reflect the significant progress Citi has made since Moody’s last rated Citi more than two-and-a-half years ago.”

And Moody’s lowered its rating on Wells Fargo’s senior debt to A2 from A1. Its Prime-1 short-term rating was affirmed. Its shares were up 0.8 percent in afternoon trading.

In June, the ratings agency had put Bank of America, Citigroup and Wells Fargo on review for a possible downgrade.