Microsoft was too slow to embrace the mobile phone, and was too preoccupied with Windows, which held it back,has admitted.
But, ever the optimist, he said Microsoft's small market share in mobile meant there are plenty of opportunities for growth, the BBC reports. Ballmer was speaking to Wall Street investors and analysts. He possibly wasn't doing his jumpy shouty thing he's so well known for.
"I regret that there was a period in the early 2000s when we were so focussed on what we had to do around Windows that we weren't able to redeploy talent to the new device called the phone," Ballmer said.
"That is the thing I regret the most. It would have been better for Windows and our success in other foreign factors."
Funny, I thought.
Earlier this month,, which should bolster its mobile offering. Its Windows Phone 8 mobile operating system has struggled in the face of stiff competition from the likes of Android and iOS.
But not as much as its Surface tablet. Microsoft will unveil the new Surface on Monday. The current model hasn't exactly flown off the shelves. In July, Microsoft admitted it'd lost a staggering on the device, and that it'd .
That could go some way to explaining Ballmer's departure from the company. He'll step down in the next 12 months, though no successor has been announced as yet. Nokia's Stephen Elop -- an ex-Microsoft man himself -- will surely be in the running. Elop will still oversee Nokia's handsets once the deal is done and the Finnish phone firm has been subsumed by Microsoft early next year.
Are you a fan of Windows Phone 8? How will the Nokia deal affect it? Let me know in the comments, or on our Facebook page.