City trailed United by eight points with six games to go on the way to winning the title last season, and Aguero is confident that his side can again recover from their deficit.
"We won the title off them last season and now we're in the fight again," Aguero said. "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 teammates in the dressing room, in training and in the matches. I hope that the title we won last season was just the first step."
City travel to Stoke City in the fourth round of the FA Cup on Saturday.