(Bloomberg) -- Apple Inc. will begin mandating frequent Covid-19 testing for U.S. employees who aren’t vaccinated, while letting inoculated workers get checked less often. 

The push, which begins next month, will apply to U.S. offices and stores, the company told employees at a meeting Friday. Apple said it’s assessing its policies on a country-by-country basis, but Chief Executive Officer Tim Cook urged workers to get the vaccine.

The iPhone maker has gradually tightened Covid policies, while still stopping short of requiring all employees to get the shots. It previously asked U.S. workers to report their vaccination status. And the company ramped up its optional Covid-19 testing program last month, requesting that employees use it up to three times per week.

An Apple spokesperson declined to comment. 

Apple also has been struggling with when to ask office workers to come back in-person. It initially aimed to have workers back in June, and then pushed that back until early September. It delayed it again until October and then until January. It has told employees it will give them a one-month warning on a return deadline.

The Verge previously reported on the testing plan.

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