By Ludwig Burger and Christoph Steitz

FRANKFURT (Reuters) -Siemens Energy on Saturday said it would offer 18.05 euros ($19.06) per share for the remaining third it does not already own in Spanish-listed Siemens Gamesa, hoping to remove a complex ownership structure that has weighed on its shares.

Siemens Energy said the bid constitutes a premium of 27.7% over the last unaffected closing share price of wind turbine maker Siemens Gamesa Renewable Energery, also known as SGRE, of 14.13 euros on May 17.

The offer values all the Spanish-German company’s equity at about 12.3 billion euros, and the targeted stake at 4.1 billion.

Siemens Energy has faced mounting shareholder pressure to seek control of Siemens Gamesa, in which it owns 67%, a stake it inherited as part of a spin-off from former parent Siemens.

That stake has given Siemens Energy little influence, however, which has become a problem in the wake of operational problems at Siemens Gamesa, which has issued three profit warnings in less than a year.

“It is critical that the deteriorating situation at SGRE is being stopped as soon as possible, and the value-creating repositioning starts quickly,” said Joe Kaeser, supervisory board chairman at Siemens Energy.

Siemens Energy said it plans to finance up to 2.5 billion euros of the transaction with equity or equity-like instruments.

The remainder would be financed with debt as well as cash on hand. As a first step, equity may be offered without subscription rights, subject to market conditions, it added.

($1 = 0.9470 euros)

(Reporting by Christoph Steitz and Ludwig Burger; Editing by Nick Zieminski and Daniel Wallis)