City pipped Liverpool to the title by a single point last term in a record-breaking title race:
After 11 games of the 2019-20 campaign, Liverpool have a six-point lead over the Sky Blues at the top of the table, and the two sides meet at Anfield on Sunday in a potentially season-defining clash:
Aguero acknowledged Liverpool must now be considered City's main challengers for England's most prestigious piece of silverware, but he said games against United remain the biggest of the lot, per France Football (h/t Will Magee of Goal):
"[The Liverpool game] may be the Clasico for television, but for us, the Clasico, it's the match against United. Liverpool have always been a tough opponent. But when I arrived, the team we were fighting for the title was United.
"Initially, it was something strange in [Manchester] that City competes against United. Then there was Chelsea. But these last four seasons, Liverpool have become a very strong team and are now fighting with us to win the Premier League.
"They are the only team in the league that can hurt us. They have been chasing a new league title for years. Last season, they didn't go all the way, so they are very motivated. This year, they are in front of us and will try to go to the end."
Aguero, 31, joined City in 2011 from Atletico Madrid for a reported fee of £38 million. Nine years on that looks like one of the best pieces of business in the club's history because the Argentinian is now City's all-time record goalscorer:
He has netted at least 20 league goals in each of the last five seasons and is well on his way to hitting that mark again in 2019-20 with nine goals in 10 appearances this term in the English top flight.
Aguero will be vital for manager Pep Guardiola on Sunday. City will be looking to beat Liverpool and close to within three points of their title rivals.
Since their shock home loss to Wolverhampton Wanderers in the Premier League on October 6, City have won five on the bounce in all competitions.
Liverpool, meanwhile, are yet to be beaten in the Premier League this term and have not lost a home game in the English top flight since April 2017, a run of 45 matches.