* Stake will fall to 12 percent initially
* Aims to build back stake to above 20 percent - deputy CEO
* PBG is not for sale
WARSAW, Sept 17 (Reuters) - Polish construction group PBG will build its Hydrobudowa stake back above 20 percent after selling a controlling interest in the unit to a buyer intent on getting a majority, a top PBG executive said.
Poland's largest listed builder will see its stake fall to 12 percent as a result of the deal, but it will add to that as a sign of its long-term commitment to Hydrobudowa, PBG Deputy Chief Executive Przemyslaw Szkudlarczyk told Reuters on Friday.
"We want eventually to raise our stake to the highest possible level, realistically 20-some percent," Szkudlarczyk said in an interview. "One of the conditions of the preliminary deal was that PBG does not exit Hydrobudowa."
The blue-chip builder said on Wednesday it planned to sell majority stakes in two subsidiaries -- Hydrobudowa and Aprivia -- for over 500 million zlotys ($166.5 million) to an undisclosed suitor.
Szkudlarczyk declined to name the buyer, who has yet to conduct due diligence on the two units, saying only it is a concessional operator specialising in roads and railways.
"Cooperation with PBG was also a condition of allowing an investor inside Hydrobudowa," the deputy CEO said. "PBG itself is not for sale. The investor will not be one of PBG's shareholders."
The deal values Hydrobudowa shares at 4.01 zlotys each, slightly above Wednesday's closing price of 3.9 zlotys. The shares were trading down 1.9 percent at 3.58 zlotys at 1230 GMT.
The sides have until March 15, 2011, to sign the final deal. Szkudlarczyk said it was "not very likely" it will be sealed this year. (Reporting by Adrian Krajewski and Pawel Bernat; Editing by Michael Shields)