A 1-1 draw away at Excelsior Rotterdam at the weekend has left Ajax six points behind leaders Feyenoord with just seven games to go.
Klaassen admits the odds are stacked against them but he remains defiant that they still have a chance and is not ready to throw in the towel.
Klaassen said: ”We have not given up on winning the title even after dropping points but we have made things much more difficult for ourselves.
”We did not play well but that is football, you have games like that like where we were not quite good enough to win the game.
”Yes, the are factors to take into account like playing last Thursday against FC Copenhagen but that is beside the point. We must be beating teams like Excelsior Rotterdam."