U.S. markets were poised to open lower Thursday as oil prices rose and treasury yields resumed their climb amid the ongoing stalemate between Iran and the U.S.Futures for the S&P 500 and Dow Jones Industrial Average each fell 0.2 per cent before the opening bell. Nasdaq futures retreated 0.4 per cent.Walmart shares slid two per cent in premarket after the retail giant delivered another quarter of impressive sales but offered up a weaker outlook than analysts were hoping for. Walmart has resonated with Americans who have grown increasingly cautious about where they spend their money with inflation taking a bigger…