Microsoft said today it would launch a tablet computer before the Christmas shopping season in an effort to take on Apple's iPad.
"You'll see new slates with Windows on them. You'll see them this Christmas," he told an audience of students, staff and journalists at the London School of Economics.
"Certainly we have done work around the tablet as both a productivity device and a consumption device," he said.
Gartner estimates 10 million tablets PCs will be sold this year as people begin adopting such devices, which include Dell's Streak and Asustek's Eee Pad. Apple's iPad has sold 3.3 million in its first quarter.
Microsoft's Windows phone software had 8.7 percent of the smartphone market last year, but that is on track to fall to 3.9 percent by 2014, according to Gartner.
"The job right now is we've got to get back seriously into the game of phones," Ballmer said.
"We've got to have a comeback against the competition and I think with our new Windows phones we really have a beautiful product."