WASHINGTON, March 22 (Reuters) - The no-fly zone over Libya could end up costing the Western coalition more than $1 billion if the operation drags on more than a couple of months, defense analysts say. Zack Cooper, a senior analyst at the Center for Strategic and Budgetary Assessments, said the initial cost of eliminating Libyan leader Muammar Gaddafi's air defenses was likely to be between $400 million and $800 million. The expense of patrolling the no-fly zone once it is established is likely to be $30 million to $100 million a week, he said. The U.S. military has no official...