Moody's on Friday downgraded its outlook on United States debt to negative from stable, one week before crucial budget negotiations in Congress.

For now, the agency has maintained its Aaa rating on US government debt.

"In the context of higher interest rates, without effective fiscal policy measures to reduce government spending or increase revenues, Moody's expects that the US's fiscal deficits will remain very large, significantly weakening debt affordability," the agency said.

The US Treasury immediately voiced its disagreement with Moody's decision.

"The American economy remains strong, and Treasury securities are the world's preeminent safe and liquid asset," Deputy Secretary of the Treasury Wally Adeyemo in a statement.

"The Biden Administration has demonstrated its commitment to fiscal sustainability, including through the more than $1 trillion in deficit reduction included in the June debt limit deal as well as President Biden's budget proposals that would reduce the deficit by nearly $2.5 trillion over the next decade."

The US budget deficit, published last month for the 2023 fiscal year ending Sept. 30, has widened to $1.7 trillion.

Due to interest rate hikes by the US central bank to curb inflation, the cost of debt for the United States has ballooned, with Washington paying $162 billion more for interest in the last fiscal year compared to 2022. Moody's is the only major agency to maintain its rating for US sovereign debt at its highest level -- underscoring the potential economic danger to the United States of failing to reach an agreement to keep the government funded in one week's time.

Neither the Democratic-controlled Senate nor the Republican-led House of Representatives has passed a bill to extend government funding, which expires at midnight next Friday into Saturday.

Without an agreement by Nov. 17, the world's largest economy would enter a so-called government shutdown. (AFP)