Europe's continuing debt troubles pushed stocks sharply lower after the opening bell in a shortened session on Wall Street.
European stock markets and the euro also fell as fears grow that Portugal will need to tap funds from the EU as its borrowing costs continue to rise.
The Dow Jones industrial average was down 107, or 0.9 percent, to 11,079. The S&P 500 index was off 10, or 0.8 percent, to 1,188.
In Toronto, the S&P/TSX composite index mirrored a fall in commodity prices, opening down 82.2 points to 12,863.7.
With files from CP/AP