Stocks are falling and bond prices are rising as tensions build over Russia's military presence in the Ukraine.
The price of crude oil rose as traders feared that Russian oil exports might be disrupted if Western governments impose sanctions on Moscow.
The Dow Jones industrial average fell 153 points, or 0.9 percent, to close at 16,168 Monday.
The Standard & Poor's 500 index fell 14 points, or 0.8 percent, to 1,845. The S&P 500 closed at a record high on Friday.
The Nasdaq composite fell 30 points, or 0.7 percent, to 4,277.
Russia's benchmark stock index plunged 12 percent. Stocks also fell sharply in Europe. Germany's DAX fell the most, 3.4 percent.
The price of gold rose to a four-month high as traders sought safety.