After their proposed merger was blocked by a federal judge, insurers Anthem and Cigna now have new opponents in court: each other.

On Feb. 14, Cigna said it was terminating the merger agreement with Anthem by filing suit against its would-be partner, arguing it had no right to extend the termination date to April 30. Cigna is seeking a total of $15 billion in damages, including the $1.85 billion break-up fee included in the merger agreement.

“These additional damages include the amount of premium that Cigna shareholders did not realize as a result of the failed merger process,” Cigna said in a press release. “This action is necessary to enforce and preserve Cigna’s rights and protect the interests of its shareholders. The company believes strongly in the merits of its case and hopes that this matter is rapidly resolved.”

This action came days after Anthem had asked for an expedited appeal of a federal judge’s decision to block the $54 billion acquisition. In its appellant brief, Anthem disputed Cigna’s right to terminate the deal and said a quicker appeal decision would prevent “risk and litigation on that subject.”

With that hope dashed with Cigna’s lawsuit, Anthem countersued on Feb. 15, asking for a restraining order to prevent Cigna from terminating the merger agreement and accusing the company of trying to undermine the deal.

“Cigna’s lawsuit and purported termination is the next step in Cigna’s campaign to sabotage the merger and to try to deflect attention from its repeated willful breaches of the merger agreement in support of such effort,” Anthem said in a press release.

Disagreements between the merger partners have been well-documented. The U.S. Department of Justice alleged before the antitrust trial that both Anthem and Cigna had accused each other of violating the terms of the agreement. Anthem had hinted at the tension in court filings, repeatedly arguing for a speedier trial or else Cigna would try and back out of the deal.

Anthem believes the merger is still possible. In its press release, it outlined several “integration efforts” in which Cigna has supposedly refused to participate, like meetings between senior management, efforts to expedite discovery in the trial, or to even acknowledge the extension of the merger agreement.

Cigna’s decision to file a lawsuit regarding the termination date, Anthem argued, will undermine their chances for an expedited appeal.

“Cigna severely damages the opportunity to obtain expedited appellate review by wrongfully purporting to terminate the Merger Agreement before the DOJ’s opposition to Anthem’s motion to expedite the appeal is due,” Anthem said.

The response from Cigna was to call Anthem’s claims “meritless,” arguing that with the U.S. District Court ruling, there’s no viable way to move forward with the merger.