A US import ban on certain Apple smartwatch models came into effect Tuesday, after the Biden administration opted not to veto a ruling on patent infringements.

The United States International Trade Commission (ITC) decided in October to ban Apple Watch models over a patented technology for detecting blood-oxygen levels.

Apple contends that the ITC finding was in error and should be reversed, but last week paused its US sales of Apple Watch Series 9 and Apple Watch Ultra 2.

The iPhone-maker said it would appeal the decision in a US federal court.

The move came into effect on the online Apple Store on December 21, with retail locations ceasing sales December 24—just ahead of the holiday.

The order stemmed from a complaint made to the commission in mid-2021 by Masimo Corp, in which the medical device maker accused Apple of infringing on "light-based oximetry functionality."

Masimo contends it invented the technology—and that Apple poached its employees to win access to the knowledge.

"After careful consultations, Ambassador (Katherine) Tai decided not to reverse the... determination and the ITC's decision became final on December 26, 2023," the office of the US Trade Representative said in a statement on Tuesday.

Though the US president has authority to reverse import bans, such actions are only taken rarely.

Apple has been steadily ramping up fitness and health features with each generation of its Apple Watch, which dominates the smartwatch category.

In September, Apple released its Apple Watch Series 9, touting increased performance along with features such as the ability to access and log health data.

"We strongly disagree with the USITC decision and resulting exclusion order, and are taking all measures to return Apple Watch Series 9 and Apple Watch Ultra 2 to customers in the US as soon as possible," Apple said in a statement Tuesday.

At the time of the original decision, Apple said Masimo had "wrongly attempted to use the ITC to keep a potentially lifesaving product from millions of US consumers while making way for their own watch that copies Apple."

In May, a trial of Masimo's allegations ended in a mistrial after jurors failed to reach a unanimous verdict.

Late last year, Apple filed two patent infringement lawsuits accusing Masimo of copying Apple Watch technology.

In November, Masimo was cleared by US regulators to use its own wrist-worn product for prescription and over-the-counter use.

Apple has argued that the company is using litigation to make way for its own Apple Watch-inspired products.

© 2023 AFP