Apple has filed another complaint against HTC with the International Trade Commission, alleging patent infringement by the Taiwanese smartphone and tablet maker.
A notice on ITC's website said that Apple had filed a complaint against HTC under Section 337 of the Tariff Act of 1930, which includes allegations of "patent infringement and trademark infringement by imported goods."
An ITC spokesman said the complaint was filed by Apple on Friday, but has not yet been posted to the website because the documents were under review.
HTC, which is based in Taiwan, is denying all of Apple's past and present claims and will continue to protect and defend its own intellectual property. "HTC is dismayed that Apple has resorted to competition in the courts rather than the marketplace," said Grace Lei, general counsel of HTC.
Apple did not respond to a request for comment.
Both companies have been fighting a patent battle since last year. Apple has filed multiple lawsuits against HTC, including a suit in March last year for allegedly infringing on 20 patents. HTC in May last year filed a complaint against Apple with the ITC for infringing on five patents, and asked to halt the importation and sale of the iPhone, iPad and iPod into the US.
Apple has also exchanged suits with top phone maker Samsung, which makes Android phones and devices.
HTC is also bulking up its intellectual property portfolio through acquisitions. HTC last week said it would acquire graphics chip maker S3 Graphics from Via Technologies for $300 million (£190 million). HTC in the process will get S3 Graphics' portfolio of 235 patents and pending applications, including many related to graphics.
On July 1, an ITC judge ruled that Apple infringed on some of the claims contained in two S3 Graphics patents, including US Patent No. 6,658,146, directed to systems and methods for compressing images, and US Patent No. 6,683,978, directed to image data formats.
Overall, global mobile phone sales totalled 427.8 million units in the first quarter of 2011, an increase of 19 percent compared to the first quarter of 2010, according to research firm Gartner. Nokia and Samsung were the top smartphone vendors while Apple was in fourth place, with sales of 16.9 million units, and HTC was in seventh place, selling 9.8 million units.