US stock futures drift higher;
US stock index futures drifted higher Tuesday, shaking off a weaker tone in Europe and Asia on growth concerns, as investors keep their focus on Federal Reserve Chairman Ben Bernanke's Friday speech in Jackson Hole, Wyo.
US stock index futures drifted slightly lower Monday as investors weighed prospects the Federal Reserve will deliver a further round of monetary stimulus this week, while also factoring in a mixed round of Chinese economic data and potentially market-moving events on the European calendar.