In court documents that surfaced on Tuesday, Qualcomm says new evidence shows Apple made improper use of its modem technology to help Qualcomm rival Intel develop a more competitive alternative.

Qualcomm accuses Apple of stealing its trade secrets and giving them to Intel to improve its chips, paving the way for Apple to use them instead of Qualcomm chips.

In the new filings, Qualcomm says that, at Apple's request, it allowed the iPhone maker deep access to its software and tools, but with strict limits on how those products could be used. Rather than just use it to improve the performance and functioning of Qualcomm chips, the company alleges that Apple used it to understand how the modem works and to help Intel improve their chips.

Qualcomm made the accusations in a motion to amend a complaint filed in November, when it alleged Apple had broken a software license contract by sharing confidential details about Qualcomm's chips with Intel engineers.

Qualcomm provided modem chips for the iPhone, which helped the device connect to wireless data networks. Starting with the iPhone 7, however, Apple began using Intel modem chips in some of its models.

Both Apple and Intel declined to comment.

Last month, Apple alleged that Qualcomm had refused to answer its questions about which specific confidential information it had improperly shared with Intel. Apple also alleged at the time that it had given Qualcomm the chance to verify that Qualcomm's software had been used properly.

In a wide-ranging legal dispute, Apple has accused Qualcomm of unfair patent licensing practices. Qualcomm, the world's largest mobile phone chipmaker, has in turn accused Apple of patent infringement.

It will be up to the judge whether to allow Qualcomm to update its lawsuit to include the new claims. If she does allow the change, that might delay the case's planned April 2019 trial.