"We have got to make things happen with Windows 7 on slates," Ballmer told financial analysts at Microsoft headquarters in Redmond, Washington, during a meeting that was streamed live on the Web.

"It is job one urgency around here, nobody's sleeping at the switch," he said of developing rival devices to Apple's popular iPad.

"We've got to push right now, right now with our hardware partners," he said. "Some of you have said well 'When? When?' - as soon as they're ready they'll be shipping."

Ballmer said Microsoft is working with its hardware partners, which include Hewlett-Packard, Lenovo, Asus, Dell, Samsung, Toshiba, and Sony, "not just to deliver something but to deliver products that people really want to go buy."

Ballmer doled out grudging praise for the iPad, which has quickly taken hold of what is expected to be a growing market for touchscreen computers in between a smartphone and a laptop computer.

Most of the industry refers to the devices as tablet computers but Microsoft calls them slates.

"Apple's done an interesting job of putting together a synthesis, putting a product out of which they've certainly sold more than I'd like them to sell," Ballmer said.

"We think about that in a competitive sense," he said. "We have got to make things happen, just as we had to make things happen on netbooks.

"We're in the process of doing that as we speak," Ballmer added. "We're working with our hardware partners, we're tuning Windows 7 to new slate hardware designs."