Apple’s “pinch-to-zoom” patent, which the company has used as an anchor in its legal wars against rival Samsung, was preliminarily rejected Wednesday by the U.S. Patent and Trademark Office.

The action, which Apple can challenge, dealt a blow to its ongoing battle to prove that Samsung copied the designs of the iPhone for its own Galaxy line of smartphones, which have soared in popularity and eroded Apple’s share in that market.

The patent office struck down parts of Apple’s patent, stating that previous patents claimed the same innovations, documents show. Pinch-to-zoom technology allows consumers to use their fingers directly on a screen to enlarge or minimize photos, text or maps on smartphones and tablets.

In August, Samsung was slapped with a $1 billion award by a jury in the U.S. District Court in San Francisco on grounds that it violated that patent and five others.

Since then, Samsung has been trying to persuade the court’s judge, Lucy Koh, to vacate the fine, while Apple has been calling for a retail ban on dozens of Samsung gadgets.

On Wednesday, Samsung argued that the patent office’s finding was “relevant” and that the case should be retried. The South Korean company added that the patent office’s decision should be considered as Koh weighs a sales ban on Galaxy smartphones and tablets in the United States.

Meanwhile, Apple is expected to ask the patent office to reevaluate its decision and can file comments to argue its case that it owns the now-ubiquitous pinch-to-zoom tool.

Its claim for the feature has been a cornerstone of Apple’s patent battles with Samsung in numerous courts around the globe.

Apple and Samsung are the leading sellers of smartphones, though Samsung also manufacturers and supplies parts for Apple products, including the iPhone.

Both firms declined to comment.

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