The Germany international's current deal with the Bundesliga champions is due to expire at the end of June, and the defender's future has been the subject of much speculation in recent weeks.
"The negotiations with Niklas dragged on for a very long time. We made him an offer. He didn't accept it. He wants to leave the club at the end of the season," Kahn told reporters.
"We have a certain responsibility when it comes to the offers. We have to stick to certain financial conditions. It's normal in this business that you'll not always reach an agreement."
Sule has made 25 appearances for Bayern during the 2021-22 campaign, while he has represented the club on 158 occasions in all competitions since arriving from Hoffenheim in July 2017. body check tags ::