According to Business Week's sources that are said to be familiar with the matter, Microsoft will turn up late to the battle of the tablets.

Microsoft won’t release a rival to Apple and Google tablet operating systems until the 2012 back-to- school season, says Business Week.

The report says that testing of a new version of Windows will begin at the end of this year with partners and customers.

Last year Chief Executive Steve Ballmer said Microsoft was "hardcore" about Windows 7 tablets.

"This year one of the most important things that we will do in the smart device category is really push forward with Windows 7-based slates and Windows 7 phones," Ballmer said.

Gartner analyst Michael Gartenberg said, "If 2011 is the year of the tablet wars, Microsoft will be awfully late suiting up for that battle. It’s not a good position to be in.”

Should Microsoft not make it to the tablet party until 2010, it will likely face an uphill battle against iPad 3 or even 4 and whatever Google rustles up in the meantime.