June 17 - Private equity firm Blackstone is in exclusive talks to buy Jack Wolfskin as the German outdoor brand seeks to improve its popularity outside its home country.

Negociations will go on until the third quarter of 2011

Quadriga Capital, which owns Jack Wolfskin along with Barclays Private Equity, said in a statement on Friday that all parties were aiming to conclude negotiations in the third quarter of 2011 and that the new owners would drive international expansion of the brand.

Wolfskin's owners had tried to sell the brand earlier this year but initial attempts stalled after it failed to attract a high enough offer.

A source told Reuters on Thursday that Blackstone was willing to pay more than 700 million euros ($1 billion) for the brand, whose rivals in the fast growing market for outdoor clothing and equipment include VF Corp-owned The North Face .

Sportswear makers such as Adidas and Puma were also seen as potential buyers but ruled themselves out of the process fairly early on.

(Reporting by by Victoria Bryan; Editing by Jon Loades-Carter)