SpaceX has said its U.S.-based Starlink customers will see their broadband service badly disrupted if Dish Network is allowed to use the 12GHz band for its 5G cellular network.

The decision is in the hands of the Federal Communications Commission (FCC) as Dish Network and others such as New York-based RS Access lobby the agency to let them use the 12GHz band. But SpaceX isn’t happy.

“If Dish’s lobbying efforts succeed, our study shows that Starlink customers will experience harmful interference more than 77% of the time and total outage of service 74% of the time, rendering Starlink unusable for most Americans,” the company said in a message posted on its website on Tuesday, June 21.

The long-running dispute involves a number of companies that are trying to gain access to the 12GHz band that SpaceX already uses for its internet-from-space Starlink service.

Dish has previously published data suggesting that ground-based 5G networks could comfortably share the frequency with low-Earth orbit satellite networks operated by the likes of SpaceX for its Starlink service.

But this week, SpaceX said that technical studies “dating back as far as 2016” suggest that opening up the band to ground-based 5G networks could adversely impact its Starlink service, and it even accused Dish of attempting to “mislead the FCC with faulty analysis in hopes of obscuring the truth.”

The company led by billionaire entrepreneur Elon Musk also shared a 12-page technical analysis explaining how mobile services envisioned by Dish would “cause massive disruptions to users of next-generation satellite services,” such as Starlink.

It explained that a high-gain antenna, like the SpaceX user terminal, is “designed with sufficient sensitivity to receive very weak signals coming from a desired transmitter,” adding that “such antennas do not, however, ‘reject’ interference coming from other directions.” The result is that interference would “completely wipe out the desired signal.”

In widely reported comments, a Dish spokesperson said its “expert engineers are evaluating SpaceX’s claims.”

Dish announced last week that it has launched commercial 5G services in more than 100 U.S. cities — covering around 20% of the nation’s population — by using frequencies in other spectrum bands. But whether it can access the 12GHz band as part of its 5G rollout remains to be seen.

SpaceX has launched more than 2,500 Starlink satellites into orbit for its broadband service, which currently serves more than 400,000 customers in 34 countries.