(Reuters) -The U.S. Federal Trade Commission on Monday sued to block Coach parent Tapestry's $8.5 billion deal to buy Michael Kors owner Capri, saying it would eliminate "direct head-to-head competition" between the flagship brands of the two luxury handbag makers. "The proposed merger threatens to deprive millions of American consumers of the benefits of Tapestry and Capri's head-to-head competition, which includes competition on price, discounts and promotions, innovation, design, marketing and advertising," the FTC said. The FTC's rare antitrust challenge against a high-end fashion merger could set a precedent for luxury deal regulation, several antitrust lawyers said.