It’s a full fledged battle between the long-standing partners, Qualcomm Inc. (QCOM) and Apple Inc. (AAPL).

It has been less than three months since Apple filed a $1 billion lawsuit against Qualcomm alleging that the chipmaker charged royalties on technology it had nothing to do with. It was followed by two more antitrust lawsuits filed by Apple’s Chinese subsidiary against the chipmaker over allegations that Qualcomm "abused its clout" in the industry and the company failed to meet its promise to economically license its patents. (See also, Apple Sues Qualcomm in China for 1 Billion Yuan.)

In response, Qualcomm has now countersued Apple. In a statement, the company said it seeks "damages from Apple for reneging on its promises in several agreements and to enjoin Apple from further interference with Qualcomm’s agreements with the companies that manufacture iPhones and iPads for Apple." Apple has been accused of breaching agreements, encouraging regulatory attacks on Qualcomm’s business with false statements, misrepresenting the performance disparity between iPhones using Qualcomm modems and those using competitor-supplied modems, and interfering with Qualcomm’s long-standing agreements with Qualcomm licensees.

"Apple could not have built the incredible iPhone franchise that has made it the most profitable company in the world, capturing over 90 percent of smartphone profits, without relying upon Qualcomm's fundamental cellular technologies. Now, after a decade of historic growth, Apple refuses to acknowledge the well established and continuing value of those technologies," said Don Rosenberg, executive vice president and general counsel of Qualcomm.

Qualcomm earns profit by selling the processor chips, as well as by earning royalties on the sale of any gadget that is based on its technology. Such licensing deals account for around a third of Qualcomm’s revenues. Following the Apple’s lawsuits few months ago, Qualcomm CEO Steven Mollenkopf had mentioned in February that he prefers the matter to get sorted mutually between the two long-standing partners. However, the countersuit indicates that all is not well between Apple and Qualcomm. (For more, see Qualcomm CEO: Apple Lawsuit Will Be Settled.)

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