U.S. stocks fell on Thursday as investors raised cash ahead of a critical speech from Fed chairman Ben Bernanke, hoping he will give them a clearer picture of the Fed's plans for the struggling economy.

The Dow Jones industrial average <.DJI> was down 170.81 points, or 1.51 percent, at 11,149.90, according to the latest available figures. The Standard & Poor's 500 Index <.SPX> was down 18.34 points, or 1.56 percent, at 1,159.26. The Nasdaq Composite Index <.IXIC> was down 48.06 points, or 1.95 percent, at 2,419.63.

(Reporting by Angela Moon, Editing by Kenneth Barry)