Qualcomm Inc. QCOM -1.12% fired back at Apple Inc. AAPL -0.53% in their legal battle, defending its business model and seeking damages from Apple over withheld payments for technology used in iPhones.

Qualcomm, whose chips and patents are widely used in smartphones, accused Apple of mischaracterizing the chip maker’s business and encouraging international regulators to attack it.

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A favorable judgment on that motion could undermine Apple’s suit, said Mark Lemley, director of the Stanford University program in Law, Science & Technology, since “they’re based on similar allegations.”

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If Apple’s case proceeds, it may take as much as two years to reach a judgment, Mr. Lemley said, after which appeals might begin.