According to CNBC, Apple claims Qualcomm charges five times more for its patents than all of the other licensors it does business with combined. The company also argues that Qualcomm withheld nearly $1 billion in payments when Apple cooperated with South Korean authorities as it investigated the company's unfair trade practices -- precisely what the US and Apple are going to court over now. In December, South Korean regulators fined Qualcomm a record $854 million for abusing its power in the smartphone chip market and overcharging device makers.

"We are extremely disappointed in the way Qualcomm is conducting its business with us and unfortunately after years of disagreement over what constitutes a fair and reasonable royalty we have no choice left but to turn to the courts," Apple says in a statement to CNBC.

We've reached out to Qualcomm for comment and will update this story as we hear back.

Update: Qualcomm offered Engadget the following statement:

"While we are still in the process of reviewing the complaint in detail, it is quite clear that Apple's claims are baseless. Apple has intentionally mischaracterized our agreements and negotiations, as well as the enormity and value of the technology we have invented, contributed and shared with all mobile device makers through our licensing program. Apple has been actively encouraging regulatory attacks on Qualcomm's business in various jurisdictions around the world, as reflected in the recent KFTC decision and FTC complaint, by misrepresenting facts and withholding information. We welcome the opportunity to have these meritless claims heard in court where we will be entitled to full discovery of Apple's practices and a robust examination of the merits."