Billionaire Mark Cuban says the 'big losers' of the move to block the AT&T-Time Warner merger are Facebook and Google

Dallas Mavericks owner Mark Cuban believes Facebook and Alphabet's Google unit will be "big losers" of the Department of Justice's decision to sue to block the proposed merger between AT&T and Time Warner.

In a tweet Monday, Cuban said, "Their media advertising, content and distribution dominance will be a defense at trial. That could create bigger issues for them."

The Justice Department on Monday sued to block AT&T's $85 billion merger deal with Time Warner,calling it an "illegal" combination that harms consumers and stifles innovation, officials said.

AT&T and Time Warner announced their merger agreement last year, but the closing has been dragged out by the government's antitrust review.

A Justice Department official told reporters on Monday that the merger would raise prices for consumers and potentially block creators of media content from distributing their product without paying more money. Time Warner owns various networks in addition to CNN, including TBS, TNT and Cartoon Network. It also has lucrative sports broadcasting deals.

CNBC's Liz Moyer contributed to this report.

WATCH:  AT&T needs the Time Warner deal to try to keep up with tech giants: Mark Cuban