The University of Pittsburgh Medical Center has launched another volley in the ongoing dispute with Highmark and West Penn Allegheny Health System, filing a suit in federal court in Pittsburgh alleging that Highmark has started a campaign of false advertising in an effort to steer patients away from UPMC.

Earlier this summer, UPMC asked the court to enforce a settlement agreement between it and Highmark in a high-profile antitrust case that has been pending for years.