The winners of the last two Premier League The titles meet at Etihad on Sunday in a crunch clash at the start of the season.
Aguero has missed City’s last two games after injuring himself against West Ham last month.
The Argentine striker won’t play Olympiacos in the Champions League despite Guardiola hoping he can face the Reds.
When asked if Aguero could play against Liverpool at Etihad, Guardiola said: “We don’t know at the moment. He’s doing better, but we don’t know.
“We don’t want him to take a step back, but he’s doing better.
“It’s not as dangerous as when he felt something in the last game, the West Ham game.
“So he’s getting better. I don’t know about Liverpool but after the international break he’ll be ready for sure.
“We’re waiting for Sergio, but we were happy with Ferran [Torres]So we have an alternative. “
Aguero’s striker colleague Gabriel Jesus has also spent some time on the sidelines with an injury.
The Brazilian striker has been out since September but has returned to training with the first team.
Regarding Jesus, Guardiola added: “It’s too early to know. He’s done a training session with the team. We’re glad he’s back.”
Despite injury concerns, Guardiola has no plans to rest the Champions League players before clashing with Liverpool.
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He said: “Absolutely not. You can’t go wrong in the Champions League because we’d fight afterwards.
“We know that in the Champions League you have to secure your home games and win at least one away.
“We did that in Marseille but now we have to be sure that we can keep the points at home.
“Tomorrow we have an incredible opportunity to take a big step towards qualifying for the next round.”