The two teams meet tonight in the Champions League.
Guardiola said: "Manchester City are one of the biggest clubs in Europe. I think they have made big steps forward.
"The last two seasons they didn't get through first stage but I am 100 per cent confident they will get through to the next round.
"My impression is if they qualify, Manchester City will be one of the toughest teams in the next round.
"The same happened with Borussia Dortmund last season.
"They qualified for the next round and went on to the final."
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