First of all give full details, what is the tenure of the employee, was he/she well informed about his/her non performance have you send caution letter, have you talked with the employee and found out the reason for non performance. Also the forum is keen to know whether the thread is raised by the representative of the employer or employee himself.
The forum will not be able to advice merely on one line sentence that whether the employee can be terminated on the basis of non performance.