"We expect to become a minority shareholder and spin Osram off as soon as it is listed on the stock exchange," Siemens finance director Joe Kaeser told a telephone new conference.

Siemens announced late Monday that is would sell shares in Osram while remaining "a long-term anchor shareholder."

"The definition of a reference shareholder does not depend on the percentage of the holding," Kaeser stressed Tuesday, adding that Siemens would retain at least a "qualified minority" in Osram, but without providing details.

That could mean for example a stake of 25 percent plus one share, which allows an investor to weigh on strategic decisions.

With an estimated total value of 4.7 billion euros ($6.6 billion) for Osram, the operation is set to be the biggest in years in Germany.

A Siemens statement said: "This step will give Osram full entrepreneurial freedom to secure and further expand its leading position in a lighting market being swept by technological change.

Based in Munich, southern Germany, Osram is a leading maker of both traditional bulbs and high technology products like LEDs (light-emitting diodes) and OLEDs (organic light-emitting diodes).

It employs 40,000 people worldwide.

But although it is very profitable, the company's focus on consumer products fits poorly with Siemens chief executive officer Peter Loescher's strategy of orienting his group towards industrial clients.

Osram will also require major investments to complete the transformation of its operations to LED technology.

On Monday, Siemens said it would also create a new division dubbed Infrastructure & Cities, its fourth group of activity along with industry, energy and medical equipment.

The new unit is to begin operations in October and focus on "integrating technologies and providing tailored energy efficiency solutions for private and public infrastructures - such as intelligent building networks and integrated mobility solutions," a statement said.

Siemens estimated the Cities market at "around 300 billion euros."

Loescher was quoted as saying that "with this move, we intend to top the €100-billion mark in business volume in the next few years."

In its last fiscal year, the industrial giant posted annual sales of a little more than 75 billion euros.