Dubai is threatening retaliation against American strategic and commercial interests if Washington blocks its $6.8 billion takeover of operations at several U.S. ports. As the House Appropriations Committee yesterday marked up legislation to kill Dubai Ports World’s acquisition of Britain’s Peninsular and Oriental Steam Navigation (P&O), the emirate let it be known that it is preparing to hit back hard if necessary. A source close to the deal said members of Dubai’s royal family are furious at the hostility both Republicans and Democrats on Capitol Hill have shown toward the deal. “They’re saying, ‘All we’ve done for you guys, all...