One way that crossed my mind is to derive from the class and override the method to have private access, but it turns out that you cannot do that.
Even if you could, you probably should not be doing that anyway because it would break Liskov substitution: we expect that code that is written for a base class object would also work if that object was substituted with a derived class object.
What you can still do is use composition: wrap the class in another one that adapts to the interface that you desire.
