(Reuters) - The U.S. Federal Trade Commission sued Pepsi on Friday for offering preferential pricing to a larger retailer, whom a source familiar with the matter confirmed was Walmart.

The practices fed high consumer prices by leaving other retailers, from large grocery chains to independent convenience stores, to pay more, the FTC said.

The lawsuit filed in New York alleges that the soft drink manufacturer violated the Robinson-Patman Act, a law that went largely unenforced for decades by the federal government.

Walmart and PepsiCo ( PEP ) did not immediately respond to Reuters requests for a comment.

"The FTC's action will help ensure all grocers and other businesses-no matter the size-can get a fair shake and compete on the merits of their skill, efficiency, and talent," outgoing FTC Chair Lina Khan said in a statement.

The FTC's two Republican commissioners, including Andrew Ferguson, who will chair the commission after President-elect Donald Trump takes office on Monday, voted against the case.