Mobile phone technology firm Qualcomm is suing handset giant Nokia, alleging infringement of 12 patents.
Nokia is Qualcomm's biggest customer
Qualcomm dominates the market for both the technology and chips needed for 3G (third generation) data services such as internet downloads and video calls.
The San Diego-based firm is demanding that Finland's Nokia stops selling phones in the US that infringe its patents, and also wants compensation.
Nokia, which has complained about Qualcomm to the EU, did not comment.
Qualcomm accuses Nokia of using its CDMA 3G technology - which allows for faster data services on a mobile phone - without its permission.
Nokia is Qualcomm's biggest customer, but the two have had a strained relationship in recent times.
While most of Nokia's handset rivals use Qualcomm's CDMA chips in their handsets, Nokia has been using its own CDMA designed semiconductors.
It appears that this is at the centre of Qualcomm's legal case.
Of the patents Qualcomm lists in its lawsuit, 11 are owned directly by itself, and the other by its subsidiary SnapTrack.
Qualcomm said it had brought the lawsuit as it appeared that negotiations with Nokia on the issue had failed.
"Until recently, we had been led to believe that these issues might be resolved cooperatively and amicably," said Qualcomm senior vice president Louis Lupin.
"However, it now appears that a cooperative resolution of these issues is quite unlikely and we must move forward with the litigation in order to protect our rights and to get these issues resolved."
Nokia and other companies including Ericsson and Texas Instruments recently complained to the European Commission about Qualcomm's practices.
They allege that Qualcomm stifles competition by offering cheaper deals on licensing its technology to those companies that also agree to buy its chips.