This, in a move that could complicate President Donald Trump's efforts to cut taxes and send ripples through global markets.
Moody's first gave the United States its pristine "Aaa" rating in 1919 and is the last of the three major credit agencies to downgrade it.
Friday's cut by one notch to "Aa1" follows a change in 2023 in the agency's outlook on the sovereign due to wider fiscal deficits and higher interest payments.
"Successive US administrations and Congress have failed to agree on measures to reverse the trend of large annual fiscal deficits and growing interest costs," Moody's said on Friday, as it changed its outlook on the US to "stable" from "negative."
The announcement drew criticism from people close to Trump.
Stephen Moore, former senior economic advisor to Trump and an economist at Heritage Foundation, called the move "outrageous".
"If a US backed government bond isn't triple A-asset then what is?" he told Reuters.
White House communications director Steven Cheung reacted to the downgrade via a social media post, singling out Moody's Economist, Mark Zandi, for criticism. He called Zandi a political opponent of Trump.
--Reuters--