The United States and Britain are on their guard against attacks by al Qaeda, with anti-aircraft missiles and fighter jets on high alert in the U.S. capital and troops patrolling London’s main airport. With the Bush administration denouncing an “unholy partnership” between Osama bin Laden’s shadowy network and Iraq, soldiers joined police on Wednesday at likely targets, with tanks and armored cars deployed at London’s Heathrow airport. U.S. defense officials said jeep-borne Stinger anti-aircraft missiles had been deployed around Washington this week after reported threats from sources with ties to al Qaeda triggered an orange alert, the second-highest level. Full Story