The Justice Department is appealing a federal judge's approval last month of AT&T's $85 billion acquisition of Time Warner.

AT&T announced the deal in October 2016, but the DOJ sued to block the merger in November 2017. Judge Richard Leon approved the deal last month after a six-week trial ended in April.

The DOJ's move, announced Thursday, is surprising because Leon adamantly advised against the agency seeking a stay and said "I do not believe that the Government has a likelihood of success on the merits of an appeal," in his June 12 ruling.

"The Government has had this merger on hold," he wrote, as "the video programming and distribution industry has continued to evolve at a breakneck pace."

The Justice Department offered no additional comment beyond its filing Thursday.

AT&T, however, did have some comments harkening back to the judge's ruling. “The Court’s decision could hardly have been more thorough, fact-based, and well-reasoned," said AT&T General Counsel David McAtee. "While the losing party in litigation always has the right to appeal if it wishes, we are surprised that the DOJ has chosen to do so under these circumstances. We are ready to defend the Court’s decision at the D.C. Circuit Court of Appeals.”

During the trial held in the U.S. District Court in Washington, D.C., the DOJ argued AT&T — whose reach extends to pay-TV, wireless and Internet broadband — would have the leverage to charge rival pay-TV providers more for the right to distribute Time Warner's networks. Those higher costs would be passed on to consumers, the government said.

AT&T countered that a combined company would be better able to compete with a growing roster of online video competitors including Facebook, Google, Netflix and Apple.