U.S. tech index futures are under pressure ahead of the market open, driven by concerns over President Donald Trump's rebuffed efforts to take over the Danish territory of Greenland and the threat of mutual tariffs between the world's largest economy and a group of European nations. The Invesco QQQ Trust Series, an exchange-traded fund that tracks the tech heavy Nasdaq 100 index, is down 2% in pre market trading following the long weekend to mark Martin Luther King Jr. Day on Monday. Trump indicated he ...