A leaked document shows that Microsoft's killer app suite for Windows 8, Office 15, may not be available in time for the operating system's release later this year. That lag could deal a significant blow to Redmond's fight against Apple in the tablet market this holiday season.

Microsoft has been touting Office 15's touch-optimized interface as built from the ground up to take advantage of Windows 8's Metro interface. The pitch: Unlike Apple's iPads, Windows 8 devices will be the only tablets on the market with fully touch-capable versions of key Office apps like Word, Excel, and PowerPoint.

It's generally believed that Windows 8 tablets will be on the market in the fall. But a document posted to the Web by a Dutch Microsoft partner says that Office 15 will not be ready until early 2013--a fact that could affect Microsoft's holiday tablet sales.

Dutch developer Maarten Visser, the CEO of a project management software startup called Meetroo, said he accessed the document through a link in an e-mail earlier this month from "the Dutch Microsoft department." Visser said he assumed the information was public so he posted the document to the Web.

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"I'm a happy partner of Microsoft's for many years," Visser said in a YouTube video he made about the incident. "I never intentionally wanted to share something that wasn't ready to be shared. Of course, afterwards you can think otherwise."

According to the document, Office 15 will be generally available in early 2013. The same timeline holds for other key products, including SharePoint 15, Exchange 15, Visio 15, and Project 15. "Being an independent software vendor, I'm always curious about roadmaps," said Visser.

In addition to the Office release schedule, the document also shows vague timelines for Windows OS products. It notes the release of last year's Windows 8 Developer Preview and the 2014 end-of-service deadline for Windows XP. It does not, however, pinpoint a release date for Windows 8. It also notes "future investments" for Windows Phone in 2012. Some analysts believe that's a reference to Windows Phone 8.

A Microsoft spokesperson confirmed the authenticity of the document, which is dated Dec. 12, 2011, to multiple news outlets, but cautioned that it represents "best estimates" and is "in no way final or definitive."

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