The striker hasn’t featured for City since suffering a hamstring injury in our 1-1 draw at West Ham last month.
We face Olympiakos on Tuesday before our showdown with Liverpool at the weekend, after which we head into a two-week international period.
Pep hasn’t ruled Aguero out of the game against Jurgen Klopp’s side, but says the Argentine will certainly be back fit and raring to go for the trip to Tottenham towards the end of November.
"Right now, I don’t know [exactly when he will return]," Guardiola said. "He’s getting better but I don’t know.
"We don’t want him to have a setback but he’s getting better.
"I don’t know about Liverpool, but I think after the international break he will be ready."
Gabriel Jesus will be assessed later today before the boss decides whether he can feature against Olympiakos.
The Brazilian has appeared just once for City this season, a goalscoring display in our opening-day win at Wolves, a game that saw him leave the field with a muscle problem.
“It’s too early to know [whether Jesus can play on Tuesday],” he said.
“We will see today at the final session [before Olympiakos].
“He is better and did one session with the team, a regeneration one. We are happy he is back. But we are also happy with Ferran playing there, too.”
Meanwhile, Guardiola says Sunday’s game against Liverpool will not affect his team selection for the Olympiakos match.
City have taken six points from six in Champions League Group C, putting us in a commanding position to qualify for the last-16.
And with such a significant Premier League game lying in wait just five days later, some have suggested he could rest players against the Greek champions.
But Guardiola has rejected the idea.
“Absolutely not,” he said.
“It’s the Champions League. You cannot fake a step. If you do, you struggle.
“You know in the Champions League you have to secure home games and win at least one away. We did it, winning in Marseille.
“But we know we have to secure points at home. It would be a big step to qualifying for next round.”