Apple Inc broadened a legal attack on Qualcomm Inc, arguing to a U.S. federal court that license agreements that secure the chip maker a cut of every iPhone manufactured were invalid. If successful, Apple's attack would undermine a core tenet of Qualcomm's business model.

"Apple is trying to distract from the fact that it has made misleading statements about the comparative performance of its products, and threatened Qualcomm not to disclose the truth," Don Rosenberg, executive vice president and general counsel of Qualcomm, told Reuters in an e-mailed statement. Apple sued San Diego-based Qualcomm in January, saying the chip maker improperly withheld $1 billion in rebates because Apple helped Korean regulators investigate Qualcomm.

Apple's initial lawsuit was a relatively narrow one focused on whether it violated a contract with Qualcomm by helping regulators that were investigating Qualcomm's business practices. But the new filing expands Apple's claims and seeks to stop Qualcomm's longstanding business model using a legal theory based on a ruling last month.