The fighting, which began on Friday with a surprise Israeli attack on Iran, has been some of the fiercest and most prolonged in the decades-long enmity between Israel and Iran, raising fears of a wider war that could draw in the United States and other powers.

Stock futures wavered before Monday's session as the escalating conflict between Israel and Iran spiked oil prices and raised investors' concerns about the global economy. Dow Jones Industrial Average futures shed 56 points, or 0.1%. S&P 500 futures lost 0.1%, while Nasdaq 100 futures traded around their flatline.