Ratings agency Fitch has put the US credit on watch for a possible downgrade, raising the stakes as talks over the country's debt ceiling go down to the wire, and adding to the jitters in global markets.
Fitch put the country's "AAA" rating, its highest rank, on a negative watch in a precursor to a possible downgrade should politicians fail to raise the amount that the Treasury can borrow before it runs out of money.
This could happen as soon as next week.
A downgrade could affect the pricing of trillions of dollars of Treasury debt securities.
Fitch's move revived memories of 2011, when S&P downgraded the US to AA-plus and set off a cascade of other downgrades as well as a stock market selloff.
Stocks in Asia fell today as investors remained wary of risky assets due to the hit the global economy will take if the US government defaults.
Treasury bills maturing around June 1, the so-called X-date when the government runs out of money, have been under pressure for weeks and came in for further selling, pushing yields on securities maturing on June 1 to 7.628%.
"It's not entirely unexpected given the shambles that is the debt ceiling negotiations," said Tony Sycamore, analyst at IG Markets in Sydney. "This is not a great sign."
President Joe Biden's administration and congressional Republicans are at an impasse over raising the $31.4 trillion debt ceiling, and Fitch said its rating could be lowered if the US does not raise or suspend its debt limit in time.
"Fitch still expects a resolution to the debt limit before the X-date," the credit agency said in a report.
"However, we believe risks have risen that the debt limit will not be raised or suspended before the X-date and consequently that the government could begin to miss payments on some of its obligations," it added.
Fitch said that the failure to reach a deal "would be a negative signal of the broader governance and willingness of the US to honour its obligations in a timely fashion," and would be unlikely to be consistent with a "AAA" rating.
A US Treasury spokesperson called the move a warning and said it underscored the need for a deal.
The White House said it was "one more piece of evidence that default is not an option."
The "rating watch" indicates that there is a heightened probability of a rating change and the likely direction of such a change, and is different from a "ratings outlook" which indicates the direction a rating is likely to move over a one-to two-year period.
Fitch now predicts that the US government will spend more than it earns, creating a deficit of 6.5% of the country's total economy in 2023 and 6.9% in 2024.
Among the other credit ratings agencies, Moody's also has an "Aaa" rating for the US government with a stable outlook - the highest creditworthiness evaluation Moody's gives to borrowers.
S&P Global's rating is "AA-plus," its second highest. S&P stripped the US of its coveted top rating over a debt ceiling showdown in Washington in 2011, a few days after an agreement that the agency at the time said did not stabilise "medium-term debt dynamics."
Moody's previously said it expects the US government will continue to pay its debts on time, but public statements from politicians during the debt ceiling negotiations could prompt a change in its assessments.
Fitch previously put the Us on ratings watch negative in October 2013 during the debt ceiling spat at the time.