The 20-year-old South Korean has been the subject of interest from England but sporting director Frank Arnesen remains upbeat about him staying with the Rothosen
The 56-year-old, who previously worked at Chelsea and Tottenham, said that he is more than willing to offer Son a new contract, with his current deal expiring in 2014, because he knows the youngster is worth the money.
"I am confident that we have the financial resources to meet Son's demands. Of course, we have our limits, but Son is only 20 years old and a big talent. I don't have any problems with it that we have to pay up in this situation," Arneson told Bild.
The South Korean is widely seen as one of the most exciting young Asian players in the game at the moment, with Tottenham rumoured to be interested in acquiring his services, among others.
It has been a breakthrough season for Son, who was promoted to the starting line-up by coach Thorsten Fink, following the departure of first-choice strikers Mladen Petric and Paolo Guerrero in the summer.
Son made his debut for South Korea in 2010 and currently has 11 caps to his name. His one and only goal so far for his country came against India in the 2011 AFC Asian Cup.