Traders work on the floor of the New York Stock Exchange September 22, 2014.
U.S. stocks opened lower on Tuesday, putting the S&P on pace for a third straight fall, as conflict in the Middle East intensified and after the U.S. Treasury moved to curb "tax inversion" deals.
The Dow Jones industrial average <.
DJI> fell 41.16 points, or 0.24 percent, to 17,131.52, the S&P 500 <.SPX> lost 5.29 points, or 0.27 percent, to 1,989 and the Nasdaq Composite <.IXIC> dropped 11.91 points, or 0.26 percent, to 4,515.78.