Thyssenkrupp is planning to list or sell the division, which is valued at more than 15 billion euros (12.76 billion pounds). Any buyer will have to strike an agreement with IG Metall, Germany's most powerful union, as part of an acquisition.

"We want a collective bargaining agreement that includes protection of sites and employees. We will fight to get that," Susanne Herberger, who sits on the supervisory boards of both Thyssenkrupp and its elevator unit, said in a statement.

Potential buyers, including Finland's Kone, are expected to court worker representatives to improve their chances in the current auction, which could be Europe's biggest private equity deal in 13 years according to Refinitiv data.

At the same time, suitors will sound out the scope for potential cost cutting, which will make for tricky negotiations between the two parties. Labour leaders wield powerful influence over Thyssenkrupp, controlling half of the group's supervisory board.

Thyssenkrupp Elevator employs more than 53,000 people globally, of whom less than 5,000 are based in Germany. With an adjusted profit margin of 11.4%, it is by far Thyssenkrupp's most valuable asset.

(Reporting by Christoph Steitz; Editing by Michelle Martin)