REDMOND, Washington (AP) — Microsoft told employees Thursday that it has indefinitely delayed their return to U.S. offices until it's safer to do so.

"Given the uncertainty of COVID-19, we've decided against attempting to forecast a new date for a full reopening of our U.S. work sites," Jared Spataro, a corporate vice president, wrote in a blog post.

Microsoft had already postponed its planned return to the workplace from September to no earlier than Oct. 4, but now says the re-opening won't be next month.

Microsoft employs about 181,000 full-time workers, of whom 103,000 are in the U.S.

Microsoft will wait for public health guidance on when it is safe to return, Spataro said. It will then give workers a 30-day transition period to prepare.

Last month Microsoft said it will require proof of vaccination for all employees, vendors and visitors to its U.S. offices starting this fall.