The Serbian international has entered the final 12 months of his current contract and can leave the club for nothing at the end of this season.
Guardiola said: "We're in September, so we have time. What I want is that Aleksandar is happy here.
"If he plays at that level, then of course there is going to be interest in speaking to him from all the clubs in the world.
"But what I want is that now he is happy and every day he feels comfortable playing.
"He's a guy who has helped us a lot from the beginning. That is the most important thing.
"We have time to speak. But at the end of the day, the player decides. If he wants to stay he's going to stay. If he wants to leave because he wants a change, he's going to change.
"The other thing we have to improve is here. The people who want to stay then its perfect."