Haas is already the subject of legal action after firing Nikita Mazepin in early 2022.
Recently, when the Russian driver won a European Court of Justice case against his political sanctions, former F1 figure Oksana Kosachenko said the 25-year-old's next step should be to sue Haas for wrongful dismissal.
But Mazepin has now told Russian media group RBC that a lawsuit against Haas and its former boss Gunther Steiner has been underway for two years now.
"The trial continues," he revealed. "And this case has nothing to do with the decision of the EU court.
"The (Haas) case has already been considered in arbitration," Mazepin added, "and we are waiting for a decision, which, I hope, will be made soon."
Mazepin thinks his chances of returning to Formula 1 have "increased sharply" since the recent EU court decision, even though it will "not be easy".
"It's hard to get there, and even harder to get back," he said. "But when we first started suing, almost no one believed in our success.
"Therefore, no matter how absurd and funny it may sound now, I believe that my return to Formula 1 is possible. But first we need to achieve the implementation of the court decision. And that's not as simple as it seems.
"I hope that it doesn't take long and that I will have exactly the same rights to enter countries as any other driver," said Mazepin.
