WASHINGTON (Reuters) - The Pentagon (news - web sites) postponed action on $18 billion contracts for 100 Boeing Co. (NYSE:BA - news) 767 tankers until the deal is investigated following Boeing's firing of two officials for ethical violations, Defense Department officials said on Tuesday. Deputy Defense Secretary Paul Wolfowitz told leaders of the Senate Armed Service Committee in a letter dated Dec. 1 that he was ordering a "pause in the execution" of the Air Force contracts to lease and buy the mid-air refueling tankers, a major setback in Boeing's two-year effort to sell the planes. Wolfowitz said his decision...