U.S. stock futures pointed to steep losses on Tuesday as investors eyed threats to world energy supplies from the Iran war . Oil prices surged on worries that the war could clog the global flow of crude . S&P 500 futures are pointing to a decline of 1.5% at Tuesday's open, while the Dow Jones Industrial Average futures are indicating a 1.6% drop. On Monday, stocks had initially tumbled on concerns about the war's impact on energy prices, before rebounding and ending higher for the day as