Qualcomm Technologies Inc.’s patent spat with Apple Inc. is getting nastier, as the chip maker alleges that iPhone maker has ordered contract manufacturers to stop paying royalties until the dispute is resolved.

On Friday, Qualcomm’s lawyers said Apple was to blame for the company slashing $500 million from its next quarterly forecast, as a result of reduced royalties. The two companies are locked in a patent licensing dispute, with Apple claiming that Qualcomm has been charging over the odds for patents that the iPhone maker says it never even used. Last January, Apple slapped Qualcomm with a lawsuit that accuses the semiconductor giant of overcharging for chips and withholding nearly $1 billion in contractual rebate payments.

“We’ve been trying to reach a licensing agreement with Qualcomm for more than five years but they have refused to negotiate fair terms,” Apple said in a statement to Bloomberg. “Without an agreed-upon rate to determine how much is owed, we have suspended payments until the correct amount can be determined by the court. As we’ve said before, Qualcomm’s demands are unreasonable and they have been charging higher rates based on our innovation, not their own.”

Qualcomm sees things differently. The company retorted that Apple has actually been underpaying its chip suppliers for components, and ordering them not to pay it for licensing. With Apple’s backing, those manufacturers are withholding payments to Qualcomm, which means the chip maker has been forced to tell shareholders it will miss revenue targets by as much as $500 million, resulting in a 21 percent year-on-year decline.

On Friday, Qualcomm revised its third-quarter revenue estimates to between $4.8 billion and $5.6 billion, down from its earlier $5.3 billion to $6.1 billion forecast. The company also lowered its third quarter profit forecast from a range of 90 cents to $1.15 per share, to just 75 to 85 cents per share.

Qualcomm said Apple’s contract manufacturers might make a partial payment, but that whatever they did cough up would likely be insignificant in the great scheme of things.

“While Apple has acknowledged that payment is owed for the use of Qualcomm’s valuable intellectual property, it nevertheless continues to interfere with our contracts,” said Don Rosenberg, Qualcomm’s executive vice president and general counsel. “Apple has now unilaterally declared the contract terms unacceptable – the same terms that have applied to iPhones and cellular-enabled iPads for a decade. Apple’s continued interference with Qualcomm’s agreements to which Apple is not a party is wrongful and the latest step in Apple’s global attack on Qualcomm.”

Qualcomm had already warned that Apple could hurt its bottom line in its previous, second-quarter report.

Image: Qualcomm/Facebook