Guardiola was speaking ahead of their preseason friendly against Bayern Munich.
Haaland is yet to feature for the champions since his £51million move from Borussia Dortmund this summer.
According to him, Haaland just needs to reach full fitness and he will take the league by storm.
“Haaland? Once he reaches full fitness, he will be unstoppable,” Guardiola said.
On City’s chase for Brighton’s Marc Cucurella, he added: “We are in negotiations.
“If it doesn’t happen, we’ve alternatives… Cancelo, Wilson-Esbrand is a young talent, Ake can play there.”