Andre Villas-Boas shrugged off the Manchester clubs' starts to the season and insisted his Chelsea side are good enough "to grab them".
United and City head the the Premier League table after scoring a total of 25 goals in their opening three games.
Chelsea are two points adrift of their title rivals but have managed to score only five times.
"We want to grab them. We have to improve on a weekly basis," said the Chelsea manager.
"It's good for them. They've gone on to score a lot of goals and it's good for British football.
"We just hope to score one more goal than the opponents.
"Our objective is on shortening distance and not on what the others do in terms of performance."
Villas-Boas admitted the quality of Chelsea's game needed to improve ahead of Saturday's trip to Sunderland.
"I think it can be better and our objective is to transform it," he said.
"It's what people expect from us - to get fluency in the way we play.
"I'm very happy that we have been creating enough chances to win games and this is a good sign for us.
"We just need to improve on the quality and fluency of the game.
"Let's see what kind of response we have now."
Villas-Boas has options to freshen up his attack, with Juan Mata shining as a substitute against Norwich, Daniel Sturridge back from suspension, and Raul Meireles having signed from Liverpool on transfer deadline day.