Knut Giesler, vice chairman of Thyssenkrupp Elevator Technology and head of the IG Metall union in North Rhine-Westphalia state, where Thyssenkrupp is based, also said that any proceeds from a sale had to stay within the group.

"The company needs liquidity to restructure and to invest in future technologies," he said.

(Reporting by Tom Kaeckenhoff; Writing by Christoph Steitz)