The $26 billion T-Mobile–Sprint merger is facing a new and potentially devastating obstacle after 10 attorneys general from nine states and Washington, D.C., filed a federal lawsuit to block the deal.

The state attorneys general in the lawsuit, filed Tuesday, argue the bid to combine two of the nation’s four top mobile carriers would jack up prices for customers, particularly low-income consumers, and result in unhealthy market concentration.

Legal experts who spoke to The Hill said the states have a strong antitrust case, predicting the ensuing legal battle could drag on for months, if not years.

“[The case] materially increases the odds that the deal will never close,” Blair Levin, an analyst with New Street Research and a former Federal Communications Commission (FCC) official, said in an interview.

The lawsuit marks one of the first times a group of state attorneys general has sued to block a deal before the federal agencies overseeing the merger have both weighed in. The Republican-controlled FCC last month signaled it will approve the merger, but the Department of Justice (DOJ) has not yet made its decision on the deal.

More at The Hill.