Thirteen states and the federal government filed suit to block the purchase of National Beef Packing Co. by Brazil's JBS SA, contending the combined company would exert too much control over the $30 billion cattle and retail meat markets. The two companies together would create the nation's largest beef packer, slaughtering 35% of U.S. cattle. If the deal went through, 80% of the nation's domestic fed cattle packing capacity would be controlled by three companies: JBS Tyson Foods and Cargill.The sale has been opposed by cattle groups, which have zealously fought to keep open markets. JBS, which has acquired 31 companies since 1993, said it would "vigorously contest" the suit. JBS will also acquire Smithfield Beef, but the federal government will not oppose that purchase.Sen. Tom Harkin, D-Iowa, chairman of the Senate Agriculture Committee, applauded the move but said he remained "concerned over the impacts of JBS's acquisition of Smithfield's beef division on independent cattle producers." "Consolidation in the agricultural markets often comes at the expense of consumers and smaller farming operations, and the merger ought to be stopped," Minnesota Attorney General Lori Swanson said in a statement.