“The way we have played up until now will not be enough to win the title,” said the Spaniard, who succeeded Manuel Pellegrini in the summer.
The Blues last won the title in 2014.
Guardiola, who is preparing his side to face Borussia Monchengladbach in the Champions League on Tuesday, added: “Of course, we are so happy for the results, for the numbers and the way we’re playing after two months.
“But it is not enough to win the Premier League or achieve the big, big targets in the Champions League.”
Monchengladbach coach Andre Schubert described his counterpart at City as “the best there is” and said their opponents had a chance of winning titles both at home and in Europe.
“I understand they might be trying to soften expectations but they have incredible strength,” he said. “Manchester City has a great chance to win one or two trophies.”
Critics were unfair – Sterling
City winger Raheem Sterling has said some of the recent criticism he has faced is unjustified.
The 21-year-old endured a difficult Euro 2016 as England were knocked out in the last 16 by minnows Iceland.