"Their media advertising, content and distribution dominance will be a defense at trial", Cuban tweeted Monday.
U.S. Attorney General Jeff Sessions declined to say last week if anyone from the White House had discussed the merger with any Justice Department officials. "It would mean higher month to month TV bills and less of the new, developing inventive choices that customers are starting to appreciate".
Monday's announcement comes two weeks after a controversy erupted publicly over whether AT&T would have to sell off CNN to sidestep government concerns about the company's plan to buy Time Warner.
AT&T, which sees the deal as a way to compete against emerging technology companies such as Netflix Inc and Amazon.com Inc's Prime Video, described the lawsuit as "a radical and inexplicable departure from decades of antitrust precedent". At the same time, the DOJ argues that the proposed merger is unprecedented in its size and harm.
Consumer advocates have also been advocating against the approval of the merger, warning about the harms of continued consolidation in the telecom and media industries.
In statements to the Justice Department, AT&T said specifically that distributors who control popular programming "have the incentive and ability to use that control as a weapon to hinder competition", the official quoted AT&T as saying verbatim.