This is what you need to know before the bell:
1. U.S. stock futures were slipping and European and Asian stocks traded mixed as the same geopolitical tensions felt by investors on Monday fed into further nervousness on Tuesday.
2. Qualcomm (QCOM) filed a counterclaim to charges against it that Apple (AAPL) made in January, saying the iPhone maker "breached agreements" with the chipmaker and "encouraged regulatory attacks on Qualcomm's business in various jurisdictions around the world by misrepresenting facts and making false statements."
3. Supplier Dialog Semiconductor (DLGNF) plunged more than 30% at one point Tuesday amid concerns that the world's biggest technology company was looking to start its own chip business.
4. Shares of Whole Foods Market (WFM) jumped 10% on Monday after activist investor Jana Partners' Barry Rosenstein launched an insurgency campaign at the organic grocer, seeking to press the company to consider selling itself and make other share-price improving changes.
5. Shares of United Continental (UAL) , the parent of United Airlines, were tumbling more than 5% in premarket trading on Tuesday, after a video of a passenger being violently ejected from one of United's planes on Sunday went viral.