The 32-year-old will leave City this summer after his contract expires.
And respected Spanish journalist Guillem Balague says the Argentine is already in talks with Barca.
"It's not done yet but everybody wants it to happen," said Balague.
"The club and Aguero's camp are talking.
"They know they have to cut costs and are doing four different independent audits to see how much money there is, which then means they will know what kind of contract proposal they can put to Lionel Messi.
"But amid that backdrop they are looking for opportunities in the market. Aguero is free and would be an improvement on Martin Braithwaite. They have to sell a lot of players and they will try to do so but this would mean they have the certainty of a goalscorer."