Microsoft had some lofty predictions for Windows 10, predicting in April 2015 that its latest operating system would hit one billion devices by 2018. The company has now been forced to backtrack on this forecast thanks to the less-than-stellar performance of its Windows Phone business, ZDNet reports.

There are currently around 350 million devices running Windows 10, Microsoft's one-size-fits-all operating system that's equally aimed at PCs, laptops, tablets, games consoles and the various wearables and smart devices peppering Microsoft's ecosystem. Windows Phone was also intended to make up a fair chunk of the install base, but with the division's revenues in freefall and Windows 10 so far having done little to stem its decline, Microsoft is now waking up to the fact that Windows Phone cannot be relied upon to significantly boost the OS's adoption.

A Microsoft spokesperson said in a statement to ZDNet: "Windows 10 is off to the hottest start in history with over 350m monthly active devices, with record customer satisfaction and engagement. We're pleased with our progress to date, but due to the focusing of our phone hardware business, it will take longer than FY18 for us to reach our goal of 1bn monthly active devices."

Microsoft has made headlines for its unrelenting marketing of Windows 10 since its release in July 2015. This will presumably come to an end on 29 July, at which point users will no longer be able to upgrade to Windows 10 free of charge. As a result, the company will have to start relying on new devices, rather than updates, to make up the majority of Windows 10 installs.

Regardless, Steve Kleynhans, vice president of Gartner's Mobile and Client Computing Group, said Microsoft's 1bn devices figure was an arbitrary target intended meant to spur interest from developers.

"Windows 10 will still hit 1bn users, but whether it happens in 36 months or 48 months is really kind of unimportant," he told IBTimes UK. "The key point is, it already has hundreds of millions of users after the first year, and that is something no other version of Windows has ever accomplished.

"Windows 10 is proving to be pretty successful, and I think Microsoft admitting it won't hit the number at this point is a move to take the focus away from the goal, and put it back on the product".

The next major update to Microsoft's operating system arrives on 2 August, courtesy of the Windows 10 Anniversary Update.