The U.S. Justice Department said Thursday that it would appeal a federal judge's approval of AT&T Inc.'s $85.4 billion acquisition of Time Warner.
The Justice Department opted in June not to seek an immediate stay of the court's approval of the merger, allowing the merger to close on June 14. The department still had 60 days to appeal the decision.
The government's court filing did not disclose on what ground it intended to challenge the approval.
AT&T and the Justice Department did not immediately comment.
AT&T shares fell 1 percent after the bell.
The merger, announced in October 2016, was opposed by President Donald Trump. AT&T was sued by the Justice Department but won approval from a judge to move forward with the deal in June following a six-week trial.
Judge Richard Leon of U.S. District Court for the District of Columbia ruled that the tie-up between AT&T's wireless and satellite businesses and Time Warner's movies and television shows was legal under antitrust law.
The Justice Department had argued the deal would harm consumers.