Siemens AG, Siemens Mobility, and the majority stake in Siemens Healthineers are "the core of Siemens, that's non-negotiable", said Juergen Kerner, an IG Metall board member who is also a supervisory board member, at a press event late on Tuesday.

Joe Kaeser, predecessor of Siemens boss Roland Busch, had split off the energy technology division Siemens Energy and brought Siemens Healthineers on the stock exchange.

There will always be minor portfolio changes within the divisions, said Kerner. "That's always been the case at Siemens. We don't oppose change. It just can't be a one-way street."

(Reporting by Alexander Huebner, Writing by Miranda Murray; Editing by Madeline Chambers)