Microsoft boss Steve Ballmer has admitted to a French news site that sales of its flagship Surface tablet have gotten off to a "modest" start.

The $499 device, Microsoft's first tablet, sold out within the first 24 hours of its release for pre-order back in October. However, there are no exact details on how many the company had in stock to begin with, and Ballmer did not disclose any sales figures, so it's not known whether those sales mean the device has been a success.

Ballmer told Le Parisien, "We've had a modest start because Surface is only available on our online retail sites and a few Microsoft stores in the United States."

He quickly changed the subject and said sales would pick up for the January launch of the Intel-based tablet, the Surface Pro, which will feature a 1920x1080 10.6-inch screen, up to 128GB storage, and a better battery.

The upgraded devices will also be capable of running Windows 8 Pro and existing Windows 7 apps.

However, Microsoft has since issued a statement clarifying Ballmer's comments.

"When asked about Surface, Steve's use of the term 'modest' was in relation to the company's approach in ramping up supply and distribution of Surface with Windows RT, which has only been available via our online store and Microsoft retail and holiday stores in the US and Canada," said the company. "While our approach has been modest, Steve notes the reception to the device has been 'fantastic' which is why he also stated that 'soon, it will be available in more countries and in more stores."

Ballmer is known to be cautious about sales, admitting last year that the introduction of Windows Phone 7 was like going from "very small to very small". But he did reveal this week that the company already sold four million upgrades to its much talked about Windows 8 OS in the first three days of launch.

The company is entering a busy period, after being slow to adapt to the smartphone and tablet PC led world dominated by Apple and Google's manufacturing partners. With the release of Windows 8, designed to seamlessly integrate the desktop and touchscreen experience, the company also revealed new Windows phone devices made by Nokia and HTC in recent weeks.