The U.S. credit rating outlook was lowered from "stable" to "negative" this week by Moody's Investors Services as another government shutdown looms.
"Continued political polarization within U.S. Congress raises the risk that successive governments will not be able to reach consensus on a fiscal plan to slow the decline in debt affordability," Moody's said in a statement.
It added, "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’ fiscal deficits will remain very large, significantly weakening debt affordability."