Both Boeing Co. and Northrop Grumman Corp. went on the offensive Tuesday with media briefings designed to shore up support for missile defenses. With $6 billion in contracts on the line, Northrop's briefing stressed the need for "mobile, global, flexible missile defense" -- the criteria set forth on Monday by the vice chairman of the Joint Chiefs of Staff. "We recognize that the missile defense budget is going to come down," a Northrop executive told reporters. "We think we have wise choices for the future." Boeing, meanwhile, warned that budget cuts could endanger 55,000 "well-paying, clean industry" jobs in 36 states.