Homogeneous Thue systems and the Church-Rosser property

Homogeneous Thue systems are considered. It is shown that if a homogeneous Thue system is not Church-Rosser, then there is no Church-Rosser system that is equivalent to it. This result contrasts with the theorems of O'Dunlaing [10, 11] showing that it is undecidable whether the congruence generated by a finite Thue system is also generated by a finite Church-Rosser system.