How to call a super method (ie: toString()) from outside a derived class

existantial question

if i have a class hierarchy like:

public class TestSuper {
    public static class A {
        @Override
        public String toString() { return "I am A"; }
    }
    public static class B extends A {
        @Override
        public String toString() { return "I am B"; }
    }
    public static void main(String[] args) {
        Object o = new B();
        System.out.println( o ); // --> I am B
        // ?????? // --> I am A 
    }
}    

From the main method, is it possible to call the toString of A when the instance is of type B ???

of course, something like o.super.toString() doesn't compile ...