DT's T-Systems Division aims to make the services available any time, on any device.
The portal and Web services will be branded T .Net, and will be open to other mobile communications operators and providers of Web services, according to DT Chairman Ron Sommer.
"We have very much a shared vision of what can happen in the wireless arena," Ballmer said.
Ballmer also announced that SAP would embrace the .net platform, integrating .net with SAP Web Application Server and releasing an SAP portal development kit for .net and an SAP .net connector for Visual Studio.net.
"This builds on a very strong partnership that we already have with SAP," Ballmer said.