Ferguson: City will keep spending
Ferguson's Manchester United side, the only unbeaten team in the top flight this season, face City at Eastlands on Wednesday with a three-point lead over their rivals.
The United manager said the fact both clubs are now challenging for the title will add extra spice to the contest.
Ferguson told Inside United: "It does put an edge on [the game]. I don't believe there's any question about that. We know the kind of money they're spending - they've bought another five or six players in the summer and they'll keep doing that until they win something.
"You know that's going to be the way it is and you have to deal with it as it comes along. They're up there [challenging for the title], and you can't wait until tomorrow when there's something there today. I'm sure they're thinking that way themselves."
Neither side is playing well, but both go into the game on the back of victories after Park Ji-sung's injury-time goal saw United beat Wolverhampton Wanderers 2-1 at Old Trafford, while City arrested a run of three straight defeats by winning 2-0 at West Bromwich Albion yesterday.
"It was really important we beat West Brom because it's very difficult for a team with aspirations of challenging at the top to lose three games in a row," defender Kolo Toure said. "This win has made us very happy and put us in the perfect frame of mind ahead of Wednesday's derby."
City will be without striker Mario Balotelli, who scored both goals at West Brom before being sent off, after opting not to appeal against the Italian's dismissal.