U.S. District Judge Richard Leon of the District of Columbia struck an ominous tone in his first hearing in the Justice Department's antitrust case against AT&T's merger with Time Warner.

Leon set a March 19, 2018, trial date, which he expects to last about three weeks. The parties had disagreed over a trial date, with the government pushing for a May date and AT&T requesting a trial in February in order to get an opinion by the April 22 merger deadline. Leon told AT&T's lawyers, led by O'Melveny and Myers partner Daniel Petrocelli, their deadline was “not realistic,” and the lawyers would need to talk to their clients about moving it.

In addition, Leon urged the parties to keep motions to a minimum, and said he will require them to hold pre-motion conferences to try to “work it out” among themselves before filing motions.

“It's going to get a little crazy around here, from my perspective,” the judge said.

Leon also said he will hold status conferences every two weeks because the case is “that important.” He set the next conference for 3 p.m. Dec. 21. Leon added he will not be “receptive” to lawyers requesting to reschedule or cancel hearings or conferences because of vacation days or holidays.

“The people who are in are all-in,” Leon said. “This is not going to be easy.”

Craig Conrath, the lead lawyer for the Justice Department, spoke only to thank the judge and introduce him to various DOJ officials in the courtroom audience, including Makan Delrahim, the antitrust chief. When Petrocelli took the stand, he echoed Conrath, thanking the judge.

The DOJ sued AT&T last month, alleging the merger with Time Warner would harm consumers because it would allow the companies to charge content distributors more to host Time Warner channels and programs. The move came as somewhat of a surprise to legal circles, as the DOJ has not challenged a vertical merger in decades. AT&T pushed back on the accusations in its reply, arguing that the DOJ's concerns were not rooted in fact.

Leon himself is no stranger to such cases. He oversaw the 2011 merger between Comcast and NBC, though in that case, the DOJ did not sue. Still, Leon was critical of the deal the companies struck with officials.