U.S. stocks ended marginally lower on Tuesday as investors found little reason to push stocks higher and volume slowed dramatically as the year-end approached.

* The Dow Jones industrial average dropped 1.67 points, or 0.02 percent, to end unofficially at 10,545.41. The Standard & Poor's 500 Index dipped 1.58 points, or 0.14 percent, to finish unofficially at 1,126.20. The Nasdaq Composite Index slipped 2.68 points, or 0.12 percent, to close unofficially at 2,288.40.

* The drop halted a six-day advance in all three indexes.