Research In Motion (RIM), the maker of the handheld Blackberry phone and e-mail device, and Motorola have sued each other over patent infringements.
RIM has accused Motorola of breaching a contract by charging excessive licensing fees for essential wireless technology, court filings show.
The filing came after Motorola filed a lawsuit against Canadian RIM, accusing it of violating some of its patents.
At the heart of the dispute is a cross-licensing deal that has lapsed.
Ontario-based RIM says US mobile phone firm Motorola is obliged to negotiate reasonable terms to extend the agreement beyond January 2008.
Soured relationship
Motorola said in a statement: "Our agreement with them [RIM] expired and we have been unable to reach a suitable agreement, going forward.
"We have not yet reviewed the complaint but based on our understanding of the matter we believe their claims are entirely without merit and Motorola intends to vigorously defend itself."
The RIM products targeted in one of the Motorola lawsuits include the Blackberry 8100, 8300, and 8800 smartphone.
RIM and Motorola are rivals in the market for mobile phones which can provide several services, including wireless internet and video downloads, but have also collaborated for years.
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