The ratings agency has affirmed the long-term issuer and senior unsecured ratings of the U.S. at Aaa.

Moody's move to cut its outlook arrives as Congress faces the looming threat of a government shutdown once more. The government is funded through next Friday.

Newly elected House Speaker Mike Johnson said he plans to release a Republican government funding plan on Saturday.

Moody's Investors Service on Friday lowered its ratings outlook on the United States' government to negative from stable, pointing to rising risks to the nation's fiscal strength.

The ratings agency has affirmed the long-term issuer and senior unsecured ratings of the U.S. at Aaa.

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