Uniper's shareholders are due to vote on the motion for a special audit to investigate the role of management, filed by Elliott-backed Cornwall Luxembourg S.a.r.l. last month, at the company's annual general meeting on Wednesday.

E.ON, still Uniper's largest shareholder with a 46.65 percent stake, also plans to propose delaying the shareholder vote on whether to endorse Uniper's management, the sources said.

The endorsement vote is a standard procedure at AGMs in Germany that shows how much shareholder backing managers have.

E.ON's move, first reported by Bloomberg, would effectively pass responsibility for the vote to Finland's Fortum, which would by then own E.ON's stake in Uniper. Fortum is still waiting for Russian and EU regulatory approval of the stake acquisition.

Uniper and E.ON both declined to comment.

Uniper's supervisory board last week recommended that its shareholders reject Elliott's motion for an audit, which was filed shortly after Fortum alleged in late April that Uniper had actively worked against the proposed deal in Russia.

Due to the size of its shareholding, E.ON's voting behaviour would have been the deciding factor in determining the success of Elliott's proposal, and an abstention could have significantly increased the activist fund's chances of success.

(Reporting by Christoph Steitz; Editing by Adrian Croft)