NEW YORK (Reuters) - Sears, Roebuck & Co. and Kmart Holding Corp. on Wednesday said they would merge in an $11 billion deal to form the third-largest U.S. retailer. The companies said in a joint statement that the new company, Sears Holdings, will have about $55 billion in annual revenues, 2,350 full-line and off-mall stores, and 1,100 specialty retail stores.