Paris Saint-Germain and Barcelona have set the price for Neymar at €170 million, but details about the payments are holding up a deal, sources have told ESPN FC.
PSG want the entire amount to be paid up front, but the Catalans are exploring different ways to cover the fee following a busy summer in which they brought in Antoine Griezmann, Frenkie de Jong, Neto and Junior Firpo for a combined €239m.
During a meeting between the two sides on Tuesday, Barcelona offered to pay PSG €40m in 2019, with additional payments of €65m to be made in 2020 and 2021, but the Ligue 1 side rejected that proposal as they want the entire fee paid up front.
Barca are trying to include Ousmane Dembele as a makeweight to sweeten the deal, but there could be another stumbling block with the France international's agent, who recently said he wants the former Borussia Dortmund forward to stay at the Camp Nou.
On Wednesday, Dembele's agent Moussa Sissoko was reported by Telefoot as saying: "He is going to stay at Barca 100 percent. There is no chance he will leave. He wants to stay and he wants to win with Barca."
Sources told ESPN FC that Neymar's desire to return to Barcelona can play an important role in the negotiations, and the Brazil forward is really involved and has taken the first step to return to the club he left in 2017 after PSG paid his €222m buy-out clause.
The two clubs plan to continue talks, and sources at Camp Nou expressed their optimism on Tuesday, when they said "the transfer window is open until Sept. 2."
Another source told ESPN FC that the next 48 hours will be decisive for the negotiations.
Barcelona technical secretary Javier Bordas said after the meetings that the club "felt closer to a deal than in days past."
Sources said Barcelona thought PSG are more amenable to negotiation than in the past two occasions when the French club categorically rejected offers.
Coutinho, a player whom PSG would have been open to receiving in exchange, has since joined Bayern Munich.
Sources have told ESPN FC they need to know if they will be able to count on Neymar this season or they will have to turn to the transfer market to replace him and strengthen their attack, with Christian Eriksen, Paulo Dybala and Mauro Icardi on the club's radar.
Barca president Josep Maria Bartomeu met with his board on Monday on this new proposal, which was presented on Tuesday in Paris by directors Bordas and Andre Cury as well as Neymar's friend Alvaro Costa.
There is also interest in Neymar from Real Madrid and Juventus, though neither club has made an official bid. Neymar has told PSG that he wants to leave this summer, and the Ligue 1 side want to recoup a majority of the fee they paid two years ago.
Sources have told ESPN FC they believe the French club are in a strong position to negotiate because it was never their intention to sell a player who is under contract until the summer of 2022.
If no satisfactory offer arrives, they will look to reintegrate Neymar into the first team. He has not played since he injured his ankle in Brazil's Copa America warm-up against Qatar at the start of June.
ESPN FC correspondents Sam Marsden, Moises Llorens and Eduardo Fernandez-Abascal contributed to this report.