Pakistani drivers stand on top a tanker truck used to transport fuel to NATO forces in Afghanistan, parked near oil terminals in Pakistan's port city of Karachi, May 23, 2012. U.S. missiles fired from a drone killed four suspected militants in northwest Pakistan on May 23, officials said, increasing strains between Pakistan and the West over a six-month blockade on NATO supplies into Afghanistan. (Rizwan Tabassum/AFP/Getty Images)

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