The pricing strategies of both companies are being scrutinized under the Robinson-Patman Act, the report said.

The U.S. antitrust law prevents large franchises and chains from engaging in price discrimination against small businesses.

The FTC reached out to large retailers, including Walmart Inc, for at least a month seeking data and other information on how they purchase and price soft drinks, two of the sources told Politico. Walmart is currently not a target in the investigation, according to the report.

The FTC declined to comment, while Coca-Cola, Pepsi and Walmart did not respond to Reuters' requests for comment.