The Federal Trade Commission on Tuesday voted 5-0 to authorize filing a lawsuit to block Tempur Sealy from buying retailer Mattress Firm Group, saying the combination would suppress competitors and allow the world’s largest mattress maker to raise prices.

Lexington, Kentucky-based Tempur Sealy countered that the $4 billion purchase would drive efficiencies, not reduce competition, and said it would press on with plans to close the deal by early next year.