The Dow Jones industrial average dropped 79 points, or 0.61%, to 12,864. The Standard & Poor's 500 Index lost 8 points, or 0.59%, to 1,368. The Nasdaq Composite Index fell 16 points, or 0.56%, at 2,949.
Better-than-expected earnings from Microsoft, General Electric and Google were overshadowed by worries about Spain even though euro zone finance ministers formally approved the country's bank bailout Friday.
European stocks were broadly lower, with the Stoxx Europe 600 falling 1.0%. Spain's IBEX-35 index tumbled more than 5% and the yield on benchmark 10-year Spanish bonds rose back above 7%.
Gold lost 0.2% to $1577 an ounce, while crude-oil slumped 1.7% to $91.12 a barrel.