UPDATE 1-Petrobras says not delaying share offer again-CEO

* Petrobras CEO says not working with delay hypothesis

* Offering of up to $25 bln in new shares slated for Sept.

RIO DE JANEIRO Aug 16 (Reuters) - Brazilian state-controlled energy company Petrobras (PETR4.SA)(PBR.N) does not foresee another delay to a September stock offering worth billions, the company's chief executive officer said on Monday.

"The capitalization isn't about now; it's about the medium- and long-term," Jose Sergio Gabrielli said to reporters at an event.

Petrobras hopes next month to complete the sale of up to $25 billion of new shares to stockholders and an oil-for-shares swap with the government estimated at up to $50 billion.

The company has already delayed the plan once, and Swiss bank UBS AG (UBSN.VX)(UBS.N) said last week that it saw an increased likelihood that the transaction would be delayed beyond its current September target date. [ID:nN13138634]

The capitalization is essential for Petrobras' five-year investment plan, which would help speed the company in tapping massive offshore oil reserves.

While that oil could vault Brazil up the ranks of petroleum exporters, the commodity lies deep under the ocean, beneath a thick layer of salt, making it both technically tricky and expensive to extract. (Reporting by Denise Luna; Writing by Luciana Lopez; Editing by Gerald E. McCormick)