Stock futures fell and Treasury yields soared on Monday as investors responded to news that a major ratings agency had downgraded its assessment of U.S. federal government debt.

Futures for the Dow Jones Industrial Average dropped 250 points, or 0.58%. S&P 500 futures slipped 0.6%, while Nasdaq futures fell 0.61%. The yield on the 10-year Treasury surged 4.6 basis point to 4.485% after Moody's downgraded the U.S. credit rating one notch late Friday to Aa1 from AAA, the highest grade.

U.S. stocks open lower after Moody's stripped the U.S. of its top credit rating. Treasury yields jump as investors demand more payout to hold US debt.