Updating Records With A Incremental Number

I'm trying to update every record with a incremental number. I wrote the following query but it updates the records with the same number. Could someone please tell me what I'm doing wrong? Thanks.

declare @NextKey int
SELECT @NextKey = NEXT_KEY FROM TABLE_KEYS
WHERE TABLE_NAME = "tblEmp"
set @NextKey = @NextKey + 1

DECLARE tblNewEmp_cursor CURSOR FOR
select emp_pk from tblNewEmp

open tblNewEmp_cursor
FETCH NEXT FROM tblNewEmp_cursor
WHILE @@FETCH_STATUS = 0
begin
update tblNewEmp
set emp_pk = @NextKey
set @NextKey = @NextKey + 1
FETCH NEXT FROM tblNewEmp_cursor
end

close tblNewEmp_cursor