City have made a stunning start to the season and are on track to defend their title under Mourinho's old foe Pep Guardiola despite Chelsea and Liverpool's similarly impressive form.
Last season's derby in April saw United come from two goals down to claim a 3-2 victory, inspired by Paul Pogba's double, although Guardiola's men still secured the title later that month.
"I don't think it's special because of last season, it's special because it's the Manchester derby and it means what it means," Mourinho added.
"We are going to try. I cannot say we will be successful in our motivations and desire, but we played two difficult matches away against two very good teams, Chelsea and Juventus, and we managed to get good results.
"Even if the good results were not in our pockets the performances were there, the positive attitude was there, we are going to try. But Manchester City are a very powerful team."