Microsoft doesn't plan to challenge Apple and Google with a new tablet operating system until late next year, according to a published report.

The software giant won't release a Windows operating system tailored especially for tablets "until the 2012 back-to-school season," according to a Bloomberg report that cited people with knowledge of the company's plans. Testing with partners and customers is not expected to begin until the end of the year, according to the report.

Microsoft representatives did not immediately respond to a request for comment.

The news is a further setback for the company that dominates the PC market but is trying to break into the surging market already dominated by Apple's iOS. Apple unveiled its iPad 2 yesterday and boasted that the company had more than 90 percent market share of the tablet market. Meanwhile, the Motorola Xoom, the first tablet sporting Google's new Honeycomb OS, was released to consumers last month. (Honeycomb is based on Android, whose popularity with consumers recently made it the dominant operating system for smartphones in the U.S., according to data released today by market researcher Nielsen.)

Windows 7 is already being used on a number tablets, but that operating system's PC heritage makes it less than ideal. And with Microsoft prepping the next version of Windows to run on devices with ARM processors, the company may have a tough time persuading tablet makers to use Windows 7 on Intel's low-power x86 chips in the meantime.

In a research note released last year, Goldman Sachs pointed to weaknesses in the company's tablet strategy and mobile devices at large. "A tablet response is still not forthcoming and our early read on Windows Phone 7 has not yet changed our view that Microsoft's share in mobile OSes will remain at only the single-digit level," the research note said.

Bloomberg's report notes that Microsoft needs to update its Windows 7 operating system for tablet devices, but Business Insider reported Monday that the software giant planned to demonstrate tablets running Windows 8 by the end of June. Also, a recently leaked plan from Dell has Windows 8 tablet, code-named Peju, slated to arrive on store shelves in early 2012.