Wall Street opened lower on Tuesday, pressured by a negative outlook from Hewlett-Packard Co and weak U.S. housing data.

The declines pushed both the benchmark S&P 500 index and the Nasdaq below their 50-day moving averages, a technical symbol indicating further market weakness is possible.

The Dow Jones industrial average <.DJI> dropped 66.75 points, or 0.53 percent, to 12,481.62. The Standard & Poor's 500 Index <.SPX> lost 4.96 points, or 0.37 percent, to 1,324.51. The Nasdaq Composite Index <.IXIC> fell 12.92 points, or 0.46 percent, to 2,769.39.

(Reporting by Chuck Mikolajczak; Editing by Kenneth Barry)