"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," Ballmer was quoted as saying.
The new device, which runs a limited version of Windows and Office with a thin, click-on keyboard cover, is being positioned by Microsoft as the ideal combination of PC and tablet that is good for work as well as entertainment.
Ballmer also said 4 million upgrades to Windows 8 were sold in the three days following the system's launch.
ECONOMIC CRISIS
Asked what he thought of the re-election of U.S. President Barack Obama, Ballmer told the newspaper the $242.7 billion company would work with the president and with governments around the world on issues like data privacy, immigration of qualified engineers and patent litigation.
The launch of Windows 8 has already raised the hackles of European Union regulators, who warned Microsoft not to repeat the mistake of denying consumers a choice of rival Web browsers in its new operating system, in a dispute that has already cost the software giant more than $1.3 billion in fines.
Commenting on the outlook for the U.S. economy, Ballmer exhorted politicians to take action on the deficit, though he stopped short of saying whether more emphasis should be placed on spending cutbacks or tax increases.
"It's not about spending more or less, it's about balancing spending and income...The elections are over, it's time to get back to work," Ballmer, who took over the day-to-day running of Microsoft from its billionaire co-founder Bill Gates just over a decade ago.
