Sarah Tew/CNET

It soon may be tough to find one of Microsoft's Surface tablets, the company said.

The Surface 2 and Surface Pro 2 "are close to selling out," Microsoft's developers account tweeted earlier Friday.

At this time, it's unclear how many tablets Microsoft made and what "close to selling out" actually means. A Microsoft spokesman declined to provide information about how many devices the company built but reiterated that inventory is low at Microsoft stores and at the company's site, with some models shipping later than the slated October 22 release date.

Surface 2 and Surface Pro 2 are close to selling out. All those buyers are gonna need apps. Your move: http://t.co/YGWmjklfuB — Microsoft Developer (@msdev) October 4, 2013

A quick check in the Microsoft Store online shows the higher-end models of Surface 2 and Surface Pro 2 have shipping delays. The 64GB version of the Surface 2 won't ship until October 25, three days after it's available in stores. The 32GB version, however, will ship by October 21. The 256GB and 512GB models of Surface Pro 2, meanwhile, should ship by October 29 while the 64GB and 128GB versions ship by October 21.

In the case of its first-generation Surface RT device, Microsoft ended up building many more tablets than it could sell. In July, the company bookeda $900 million write-down for excess Surface inventory, and it also revealed that it had generated only $853 million in revenue from Surface RT and Surface Pro since their debut in the fall. Rather than dump the remaining Surface RT tablets, Microsoft continues to offer the product at a discounted rate alongside its updated devices.

iPad,

devices using Google's Android OS.

Surface tablets are Microsoft's own take on the burgeoning niche -- one that is largely dominated by Apple'sbut with a healthy dose of competition fromMicrosoft, not wanting to miss out on the tablet gravy train, opted to push Windows 8 and Windows RT through its own products. While Microsoft's first attempt last year led to disappointing results, the company is

The Surface Pro 2 is what Microsoft calls a full laptop in a tablet design, while the Surface 2 runs a stripped-down version of Windows 8. Microsoft opened preorders for the devices on September 24, and they'll hit stores October 22.

Despite the apparent strong preorders, Microsoft has faced some recent hurdles ahead of an update to its Windows operating system. Dell earlier this week became the latest company to dump plans to develop products running Windows RT, the version of Microsoft's software that runs on chips typically used in cell phones, those based on technology from ARM Holdings. The operating system has failed to gain traction with users, in part because traditional Windows programs won't run on Windows RT.

Microsoft earlier this week told CNET in a statement that Windows RT "continues to be an important element of the Windows strategy."

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Updated at 11:25 a.m. PT with comments from a Microsoft spokesman and information about availability in the Microsoft Store online.