The 46-year-old has acknowledged that last year's Champions League finalist is not big enough yet to keep its stars at the Westfalenstadion.Jurgen Klopp has admitted that Borussia Dortmund is still a selling club as it is unable to hold on to its key players.
The Bundesliga giant has lost players such as Shinji Kagawa and Mario Gotze to Manchester United and Bayern Munich in recent seasons, while Robert Lewandowski will also say farewell to BVB at the end of the 2013-14 campaign after agreeing to join the Bavarians when his contract expires in June.
Nevertheless, Klopp is hopeful that Dortmund can continue its development and become a club capable of holding on to its star men in the not too distant future.
"It has always been clear to us that our best players would be leaving at some point," Klopp told reporters. "I have already said for a few years now that it's up to us to make sure that Borussia Dortmund develop into a club where players want to go and then want to stay, too.
"However, we are not there just yet as a club. We saw this coming, but I deliberately decided to sign a new contract with BVB until the summer of 2018."
Klopp has been at Dortmund since 2008 and has since guided the club to two Bundesliga titles.