Frankfurter Allgemeine Zeitung quoted Toenjes as saying he would like Thyssenkrupp to keep a stake in its elevator division. The foundation is the top shareholder of German chemicals group Evonik.
Earlier this month, RAG told Reuters it was part of a bidding consortium which includes private equity firm Advent, Cinven and the Abu Dhabi Investment Authority.
On Thursday Reuters reported that Thyssenkrupp is nearing a full sale of its elevator division, with three people familiar with the matter saying this would secure the highest valuation of about 16 billion euros ($17.38 billion)to help the company pay down debt.
(Reporting by Michelle Martin; Editing by Edward Taylor and David Evans)