Sergio Aguero in talks with Barcelona, says Guillem Balague

Sergio Aguero is the highest-scoring overseas player in Premier League history

Manchester City striker Sergio Aguero is in talks about joining Barcelona, says BBC Sport's Guillem Balague.

Aguero, 32, will leave Etihad Stadium when his contract expires this summer after scoring 258 goals in 388 games for the club.

Barcelona have to cut costs because of financial difficulties but the lure of a proven goalscorer on a free transfer is attractive to the La Liga side.

"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."

Aguero is close friends with Messi and the pair have played together regularly for Argentina, so bringing in the fourth-highest scorer in Premier League history would help the club's negotiations with their captain, who is also able to leave this summer.

"This is not a request from Messi but it's certainly a way to convince him about what they are trying to do," added Balague. "But it's a step down from the interest they have shown in Borussia Dortmund's Erling Braut Haaland - and that is something they would like to revive if they can bring in money from outside the club."

Lionel Messi and Sergio Aguero could be joining up at club level, having often played together for Argentina

Barca boss Ronald Koeman spent two-and-a-half hours having lunch with club president Joan Laporta on Thursday.

It is not certain Koeman will still be at the Nou Camp next season and Laporta has his doubts about the Dutchman, but he has been impressed by how the manager has handled a difficult transitional year.

"While they are assessing their finances they have to be clever," said Balague. "So they have kept Ramon Planes, who is a very shrewd mover in the market and he has already prepared a detailed report on different situations: if there is no money, if the squad stays the same, if it doesn't.

"There are a bunch of players, like Memphis Depay, they can get and Aguero is one of those."

Barcelona have had a mixed season. They were eliminated at the Champions League last-16 stage by Paris St-Germain and are four points behind league leaders Atletico Madrid with two games to play, but their form in the second half of the season has improved significantly.