Nokia on Thursday filed a second complaint with the International Trade Commission (ITC) against HTC, claiming the Taiwanese smartphone company was shifting responsibility for infringement to its suppliers.
The Finnish handset maker's new ITC complaint adds another prong to it action against HTC and others it began last year.
"Nokia has filed further cases in the United States alleging that HTC products infringe additional Nokia patents," Nokia said in a statement to ZDNet.
"We began actions against HTC in 2012 to end the unauthorised use of our proprietary innovations and technologies. Since then, despite the German courts confirming infringements of Nokia patents in HTC products, HTC has shown no intention to end its practices, instead it has tried to shift responsibility to its suppliers. We have therefore taken these further steps to hold HTC accountable for its actions."
It's thought a number of patents are at issue in the case. Patents blogger Florian Mueller has dug up the list of exhibits in the ITC complaint, which shows they relate to chips made by Broadcom and Qualcomm that feature in HTC's flagship One device. If the case is successful, it could lead to the affected devices, such as the HTC One, being banned from sale.
Nokia has also filed another suit against HTC in the US District Court for the Southern District of California San Diego. The suit covers three separate patents for a "terminal, method and computer program product for interacting with a signalling tag", which Nokia claims HTC infringes in ten smartphones, including its flagship HTC One and HTC First, the phone it adapted for use with Home for Facebook.
The two new suits cover nine patents and bring the total number to 50 that Nokia has contested in courts around the world, which have most recently played out through courts in Germany and the Netherlands. Meanwhile, the hearing for Nokia's other complaint at the ITC against HTC is expected to commence this month.
ZDNet has asked HTC for comment and will update the story if it receives one.
In response to the San Diego complaint, HTC told Bloomberg that "upon receiving the official document, HTC is to consider all legal options to protect our rights".