The 30-year-old has been Barcelona's talisman for the last 13 years but is yet to renew his contract at Camp Nou.
Barca president Josep Maria Bartomeu has claimed several times that Messi's renewal has already been actioned and just needs to be announced, but no confirmation has yet been made.
In spite of the speculation surrounding Messi's future, Aguero does not think that there is much hope of his teammate coming to the Etihad Stadium, despite money not being an issue.
"The money isn't a problem here," Aguero told TyC Sport. "But I think Messi, like [Cristiano] Ronaldo, are players who are symbols of their clubs and it's difficult for them to leave.
"I would love to have Leo on my team, but that seems quite complicated."
Messi scored a hat-trick against Ecuador on Monday night to seal a 3-1 win for Argentina and qualification to the 2018 World Cup in Russia.