A lower debt rating raises the risk of higher borrowing costs for the federal government.

The warning comes as the government teeters on the brink of another shutdown next week and follows a move by Fitch ratings service just a few months ago to downgrade U.S. debt. Standard & Poor’s made a similar move more than a decade ago following an 11th hour showdown over raising the debt ceiling.

Deputy Treasury Secretary Wally Adeyemo blasted the move, saying the 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 White House placed the blame firmly on the GOP.

“Moody’s decision to change the U.S. outlook is yet another consequence of Congressional Republican extremism and dysfunction,” press secretary Karine Jean-Pierre said in a statement.

Rep. Andy Harris , a Maryland Republican and a member of the House Appropriations Committee, faulted “out-of-control government spending and deficits.”

Harris tweeted: “We cannot, in good conscience, continue writing blank checks to our federal government knowing that our children and grandchildren will be responsible for the largest debt in American history.”

The U.S. for now retains its “Aaa” rating, the highest possible creditworthiness for a borrower under Moody’s scale. The rating firm noted surprisingly strong economic growth in the U.S., which could slow the rise in its debt costs.

“The US’ institutional and governance strength is also very high, supported in particular by monetary and macroeconomic policy effectiveness,” it said.