City are in fine form and top the Premier League table ahead of Sunday's matches.
Guardiola's side have scored 11 goals in two games in England's top flight and Dunn has taken the opportunity to claim they must win the title this term, especially after spending more than £200m in the recent transfer market.
"I got a lot of reaction when I wrote [in 'The Mirror'] that he's got no excuses now, but the point I'm making is if you look at that team, you see the performance they put on and the array of attacking talent, then you see him bring on Leroy Sane, Ilkay Gundogan and Bernardo Silva," he said talking to 'Sky Sports'.
"You see those three players come on when they are 4-0 up, and those are the types of players he has at his disposal going forward. You're thinking that nothing else but winning the title would be good enough for this team.
"They spent £200m in the transfer window and there's a suggestion in the papers today that it's the most expensive squad assembled in world club football at around £400m. So no, there are no excuses. Second isn't good enough for that team. That team is an exceptional, forward-thinking team.
"You could say that Jose Mourinho has bought Romelu Lukaku and Nemanja Matic among others and spent a lot of money, so why are there no excuses for United? Well, they finished sixth last year and it's a big leap from there to first.
"Has Antonio Conte got an excuse? Possibly. He's lost a crucial player in Diego Costa and it's always hard to defend a title.
"These aren't great excuses but they are more feasible that any Pep may have. The point is that it is a reflection of how good they can play. They are the best attacking team in the Premier League by some distance."
A strong opinion from Dunn, but does he have a point? Who do you think will win the Premier League this season?