Speculation about the future of Messi has been rife for several months now after the Argentinian superstar — who scored a hat-trick to book his country's World Cup place on Wednesday — entered the final year of 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 the clock keeps ticking and that confirmation is yet to be made.
In spite of the delay, Aguero does not think that there is much hope of Messi joining him at City, even if money is not an issue for the Premier League side.
"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."
Aguero is on the sidelines after breaking a rib in a car crash in Amsterdam at the end of September, an injury which kept him out of Argentina's final two World Cup qualifiers and was expected to prevent him from playing throughout the rest of October.
The 29-year-old, though, has appeared to indicate he could be in selection content for the match against Stoke City on Saturday, while he also hit back at those criticising him for going to Amsterdam on his days off.
"I was lucky that I know the agent of Maluma [a Colombian singer], he invited me and I went. I had almost two days off and going to the airport was when I had that accident.
"Then one thinks "why did I [go]", but it's difficult to imagine that something like that could happen.
"I still do not know if I am going to play on Saturday. Today I trained normally, but without the group.
"Tomorrow I will get into the group to see how I feel, but at training it's not the same thing as a game, I want to see if I have pain."