* Fortum made 19 eur/shr bid in late July -Uniper CEO
* Approach came before last week's 22 eur/shr bid
* Fortum is "wolf in sheep's clothing" -Uniper CEO (Recasts, adds context, additional comments on deal)
DUESSELDORF/FRANKFURT, Sept 25 (Reuters) - German energy group Uniper views as "hostile" last week's takeover approach by Finnish peer Fortum, its chief executive said on Monday, disclosing that it was Fortum's second attempt to buy the firm after a rejected bid in July.
Fortum said last week it planned to buy 46.65 percent of Uniper that former parent E.ON is trying to sell, adding it would offer 22 euros a share, or 3.8 billion ($4.5 billion) for the stake, but stopping short of launching an official offer.
Sources familiar with the matter said that an official deal could be announced as early as this week, even though there was no guarantee and talks between Fortum and E.ON could still fall apart eventually.
"This is a hostile push from Fortum," Uniper CEO Klaus Schaefer said in his first interview after Fortum made the plans public, adding it was already the second time that Fortum had tried to acquire the group after a failed attempt in July.
At that time, Fortum offered 19 euros per share for at least 75 percent of the group that included plans for a domination agreement giving Fortum control and a full business integration, Schaefer said, unveiling previously unreported details of the deal.
After a thorough assessment the offer was rejected, Schaefer said, adding it would have put several thousand jobs at risk.
"Fortum had promised in July that a takeover of Uniper would be further pursued only with our consent," he said. "That was not the case - jointly with E.ON, they quietly pressed on with a deal."
A spokesman for Fortum declined to comment.
Last week, Fortum Chief Executive Pekka Lundmark said the offer was not a takeover but a "significant investment", a view challenged by Schaefer who said Fortum's goal was to acquire all of the group, not just E.ON's stake.
"It rather seems as if a wolf in sheep's clothing is standing outside our door again," he said, adding that he did not think the companies were a good strategic fit and that it was unclear to him how Fortum would fund a deal.
Sources close to the matter told Reuters that Fortum was mainly interested in Uniper's hydropower plants and interests in Swedish nuclear power stations, and it was already working with a partner that might take on Uniper's coal-fired plants.
Fortum CEO Lundmark has argued that cooperation between Fortum and Uniper "would render significant benefits for all stakeholders".
Under German takeover laws, state-controlled Fortum would have to bid for all of Uniper, as E.ON's stake is above a critical 30-percent threshold, which would value the whole group at 8.05 billion euros, below its current market value of 8.47 billion.
Currently, Uniper shares trade at 23.07 euros, above Fortum's proposed bid. They have gained a third since the 17.39 euros per share reached at the end of July.
"The current share price clearly reflects what our shareholders think," Schaefer said with regard to Fortum's offer, adding he had offered support to E.ON for a possible share placement of the Uniper stake, his favourite option, but received no answer. ($1 = 0.8416 euros) (Additional reporting by Pamela Barbaglia in London, Jussi Rosendahl and Tuomas Forsell in Helsinki; Editing by Arno Schuetze and Adrian Croft)