US stocks opened lower Tuesday amid another dramatic fall in oil prices and the Russian ruble.
Five minutes into trade, the Dow Jones Industrial Average stood at 17,109.49, down 71.35 points (0.42 percent).
The broad-based S&P 500 plummeted 22.45 (1.12 percent) to 1,979.88, while the tech-rich Nasdaq Composite Index lost 26.56 (0.58 percent) at 4,578.60.
US oil prices dropped again, sinking below $55 a barrel for the first time since May 2009. Investors have been unnerved that the steep decline in crude could signal deeper economic troubles ahead.
The Russian ruble crashed to new record lows, losing some 20 percent in value despite drastic interest rate hikes by the central bank late Monday.
The drop in the Russian currency "is messing with the US stock market's typically festive holiday spirit as it is evoking concerns about the potential for default risk, financial risk, and economic risk," said Briefing.com analyst Patrick O'Hare.
Investors are also awaiting the outcome Wednesday of a two-day US Federal Reserve meeting, with a policy announcement that could adjust the central bank's outlook for raising interest rates in 2015.