Wall Street set to snap four-day rally as worries seep in

U.S. government bond yields were at an all-time low as weak data from China added fuel to the uncertainty stemming from Britain's vote to leave the European Union. Oil prices fell nearly 3 percent as a potential economic slowdown weighed on prospects of demand. Shares of oil and gas companies including Exxon , Marathon Oil and Freeport fell in premarket trading on Tuesday.