Mark your calendars. A judge has set Feb. 13 of next year as the start date of the trial for the Justice Department’s antitrust lawsuit over AT&T’s $39 billion buyout of T-Mobile USA.

U.S. District Judge Ellen Segal Huvelle’s decision marks a compromise between the different dates proffered by AT&T and the DOJ. AT&T, anxious to get the trial underway, wanted it to begin on Jan. 16, 2012. But the DOJ asked that the date be pushed out until March 19 as it gathers evidence to support its case.

Judge Huvelle also decided against consolidating Sprint’s case with the DOJ’s at this time, but will hear from Sprint again on the matter in oral arguments scheduled for Oct. 24.

AT&T is pushing for an expedited trial as it seeks to reassure investors that it will be able to get the merger approved by regulators. The DOJ’s suit could be a nearly insurmountable hurdle for the deal. The FCC, which is also reviewing the deal, is unlikely to make a decision until the DOJ’s lawsuit clears.

The regulatory impasse could force AT&T to re-evaluate its LTE deployment strategy. The company had planned to use T-Mobile’s AWS spectrum to augment its LTE network, but won’t be able to do that as long as the merger is held up in court. The antitrust case could stretch into 2013.

Both AT&T and T-Mobile have repeatedly expressed confidence that they will find a solution to the regulatory roadblock, but it’s not clear what the companies would have to do to assuage DOJ’s concerns about the merger’s impact on competition, prices and consumer choice.

Political pressure continues to mount on both sides of the deal. Less than a week after seven state attorneys general joined the DOJ’s lawsuit against the merger, 10 state attorneys general supporting the deal sent a letter to the DOJ pressuring it to ease up on its opposition.

“It is not unusual for mergers like this to be allowed to proceed with divestitures which preserve competition and provide consumer benefits,” stated the letter, sent Wednesday by officials from Alabama, Arkansas,  Georgia, Kentucky, Michigan, North Dakota, South Dakota, Utah, West Virginia and Wyoming. “We again urge both DOJ and the FCC to focus on ways to resolve specific competitive concerns so this merger can proceed.”

Mississippi’s attorney general, who signed the group’s July letter in favor of the deal, was not listed as a signatory to yesterday’s missive.