Facing a issue while using the MERGE STATEMENT by using WEHN NOT MATCHED BY TARGET clause

Question

By using HR schema, i have created backup table (EMPLOYEES_BKP) using EMPLOYEES table. when i am using MERGE statement, i am getting the below error..

MERGE INTO EMPLOYEES_BKP BKP
USING EMPLOYEES EMP
ON (BKP.EMPLOYEE_ID=EMP.EMPLOYEE_ID)
WHEN MATCHED THEN
   UPDATE SET BKP.SALARY=EMP.SALARY
WHEN NOT MATCHED BY TARGET THEN
  INSERT (BKP.EMPLOYEE_ID, BKP.FIRST_NAME,BKP.LAST_NAME, BKP.EMAIL, BKP.PHONE_NUMBER, BKP.HIRE_DATE, BKP.JOB_ID, BKP.SALARY, BKP.COMMISSION_PCT, BKP.MANAGER_ID, BKP.DEPARTMENT_ID) 
VALUES (EMP.EMPLOYEE_ID, EMP.FIRST_NAME,EMP.LAST_NAME, EMP.EMAIL, EMP.PHONE_NUMBER, EMP.HIRE_DATE, EMP.JOB_ID, EMP.SALARY, EMP.COMMISSION_PCT, EMP.MANAGER_ID, EMP.DEPARTMENT_ID)
WHEN NOT MATCHED BY SOURCE
  DELETE;

Error at Command Line : 15 Column : 18
Error report -
SQL Error: ORA-00905: missing keyword
00905. 00000 -  "missing keyword"