NEW YORK (Reuters) - Stocks extended losses on Tuesday with the S&P 500 falling below its 50-day moving average for the first time since December 21. The Dow Jones industrial average was down 121.89 points, or 0.94 percent, at 12,807.70. The Standard & Poor's 500 Index was down 15.55 points, or 1.13 percent, at 1,366.65. The Nasdaq Composite Index was down 36.30 points, or 1.19 percent, at 3,010.78. (Reporting by Angela Moon; Editing by Jan Paschal){br}{br}View the Entire Article{br}