United have a five-point lead and the neighbours seem virtually certain to occupy the top two spots at the end of the campaign.
And Aguero, who has made a speedy recovery from the hamstring injury he picked up on New Year's Day, said: "We won the title off them last season and now we're in the fight again.
"We can regain the leadership of the Premier League from them. City have everything to continue to grow and the best is yet to come.
"I feel the ambition of my team-mates in the dressing room, in training and in the matches.
"I hope that the title we won last season was just the first step."