US technology firm Apple has appealed a federal judge's verdict in its legal battle with the video game and software developer, Epic Games, over control of the App Store.

It is seeking to overturn a ruling ordering it to loosen control of its payment options in the store.

Last month, Epic filed an appeal against the finding that it failed to prove any antitrust violations by Apple.

"We will fight on", Epic chief executive Tim Sweeney tweeted when the company confirmed its plan to contest the verdict.

Apple said in the days after the 185-page ruling by the Ninth Circuit Court of Appeals in San Francisco that it was "very happy" with the decision but had left open the door to appeal.

The companies had opted for a so-called bench trial in which a judge rather than a jury hears the evidence and decides on a verdict.

Epic launched the case aiming to break Apple's grip on the App Store, accusing the iPhone maker of acting like a monopoly in its shop for digital goods or services.

Creative Strategies analyst Carolina Milanesi said after the verdict: "For me, it is a win for Apple in that the judge clearly said they are not engaging in monopolistic behaviour.

"I don't think it is a problem for Apple from a revenue perspective."

The judge barred Apple from prohibiting developers from including in their apps "external links or other calls to action that direct customers to purchasing mechanisms."

Apple can still mandate that its payment systems is used for in-app transactions.