Published: Apr 18, 2011 10:35 PM EDT
Updated: Apr 18, 2011 7:17 PM EDT

NEW YORK (AP) - A warning from Standard & Poor's that the agency might lower its rating on U.S. government debt has sent stocks on their worst slide in a month. S&P said today there's a 33 percent chance it will lower the country's credit rating from AAA in the next two years if Washington fails to pare the country's debts.

Analysts say the new debt rating itself isn't surprising, but the markets' repsones to it are.

At one point Monday, the Dow was down nearly 230 points.  European markets lost even more.

By the end of the day, the Dow had recovered some, but not enough.  It fell 140 points, or 1.1 percent, to close at 12,202.  The S&P 500 fell 15. The Nasdaq composite fell 29.