Qualcomm  (QCOM) upped the ante in its dispute with Apple  (AAPL) over royalty fees by suing four of the company's suppliers in U.S. District Court for the Southern District of California. The companies include FoxconnCompalWistron and Pegatron

"It is unfortunate that we must take this action against these long-time licensees to enforce our agreements, but we cannot allow these manufacturers and Apple to use our valuable intellectual property without paying the fair and reasonable royalties to which they have agreed," said Don Rosenberg, Qualcomm's executive VP and general counsel.

Apple first sued Qualcomm in January, saying that the company was collecting royalty fees for "technologies they have nothing to do with." Qualcomm counter sued last month, claiming that Apple provided misleading statements to regulators in an effort to punish the company. 

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