Wall Street stocks tumbled at the open on Monday after rating agency Standard & Poor's cut the top-tier AAA credit rating of the United States, rattling already-jittery investors.

The Dow Jones industrial average dropped 227.13 points, or 1.98 percent, to 11,217.48. The Standard & Poor's 500 Index fell 20.65 points, or 1.72 percent, to 1,178.73. The Nasdaq Composite Index lost 84.81 points, or 3.35 percent, to 2,447.60.

(Reporting by Chuck Mikolajczak)