Apple faces a US ban on sales of some iPhone models after a judge said the company had violated a patent held by the microchip company Qualcomm.

A legal determination published by the International Trade Commission declared that Apple had infringed on Qualcomm technology and recommended a partial ban on iPhone imports.

The trade body itself must now determine whether to block the iPhone models, which are assembled in China, from arriving in the US.

It is uncertain whether any ban will go ahead and which iPhone models it covers, but the ruling is a legal blow to Apple as it battles San Diego-based Qualcomm in courts around the world.

The legal spat between the two has already led to sales restrictions on iPhone models in Germany and China, although Apple has been able to keep its phones on sale by adapting them. Apple, in turn, has won legal rulings saying Qualcomm owes it nearly $1bn.

In Tuesday's ruling, ITC judge MaryJoan McNamara said: “I will be recommending that a limited exclusion order together with a cease and desist order, both with certification provisions, issue against Apple."

“We appreciate Judge McNamara’s recognition of Apple’s infringement of our hardware patent and that she will be recommending an import ban and cease and desist order,” Qualcomm general counsel Don Rosenberg said in a statement.