The Catalan won the competition twice with Barcelona but has yet to do so with City, who have yet to get past the semi-finals.
Speaking ahead of their clash with Olympiakos on Wednesday, Guardiola said: ""It's not an obsession. We will try our best.
"We have an important chance to almost qualify. That's so good, to be in the best 16 teams in Europe.
"I expected a reaction after last season when we finished against Lyon in Portugal. We know what we have to do.
"The season is still young and I'm fully optimistic we are going to do a good season."