The 29-year-old, whose contract expires at the end of the season, has been linked with a number of European clubs following his exploits in recent seasons.
However, his agent Arnoldus Oosterveer has revealed that the Dutchman's future has yet to be decided.
"There is no agreement with any English club and Klaas has not yet decided anything about his future," Oosterveer told calciomercato.it.
"He has not decided if he wants to play in Italy, Spain, England or stay in Germany. He is planning his future in the winter."