At the close the Dow Jones Industrial Average was down 42.32 points (0.26 percent) at 16,066.57.
The broad-based S&P 500 fell 5.19 (0.28 percent) to 1,841.15, while the tech-rich Nasdaq Composite lost 15.02 (0.35 percent) at 4,245.40.
Tensions were rising ahead of Sunday's Crimea vote on whether to leave Ukraine and join Russia, with long talks between US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov failing to defuse the crisis.