NEW YORK — Stock futures are down sharply ahead of the start of earnings season amid fresh fears about the global economy.

Fears of a debt default have spread beyond Greece, Ireland, and Portugal to Italy and Spain. New concerns also arose over the weekend that the U.S. might fail to pay its debt for the first time in history if Republicans and Democrats cannot agree on a budget by Aug. 2.

Aluminum maker Alcoa announces second-quarter results after the closing bell, marking the unofficial beginning of U.S. earnings season.

Ahead of the opening bell, Dow Jones industrial average futures are down 102 points, or 0.8 percent, at 12,513. Standard & Poor's 500 futures are down 15, or 1.1 percent, at 1,327. Nasdaq 100 futures are down 27, or 1.1 percent, at 2,382.