Although no deal is done yet, sources said terms include an option for part-ownership of Inter Miami but would not be subsidised by the league as they did for David Beckham in 2007. When Beckham -- now a co-owner of Inter Miami -- moved to the LA Galaxy he was given the option to purchase an MLS team for a discounted price of $25 million.
ESPN also confirmed that a cut of revenue from new subscribers to Apple TV's MLS Season Pass streaming service was part of negotiations. Any agreement involving Messi and Adidas would strictly be between the player and the company, and wouldn't directly involve MLS.
Sources have told ESPN's Jordi Blanco that despite Barcelona's efforts to adjust their payroll, Messi has opted not to wait any longer and has ruled out Barcelona as a destination for next season.
Meanwhile, sources told ESPN that senior figures behind Al Hilal's attempt to sign Messi fear he has lost interest as he weighs his next move.
Media reports Wednesday said that the Argentina star has reached a deal with Inter Miami, but a spokesperson for the Major League Soccer club declined comment when asked to confirm or deny by ESPN's Jeff Carlisle.
Messi, 35, is due to become a free agent when his contract at Paris Saint-Germain expires on June 30, and the French champions announced last week that the former Barca star, who moved to Parc des Princes in 2021, will not remain at the club beyond the end of his deal.
ESPN reported in April that Al Hilal, one of four Saudi Pro League clubs taken over by Saudi Arabia's Public Investment Fund this week, had made an offer to Messi, with sources saying the club believed they had a "50-50" chance of signing the player.
But while Al Hilal's offer remains on the table, sources in Saudi Arabia have told ESPN that contact with the Messi camp has diminished and that there is a growing acceptance that the Argentine is now torn between a return to Barca, with whom he won 10 LaLiga titles and four Champions League titles before his exit to PSG, and a move to the Miami franchise part-owned by David Beckham.
One source said that the choice for Messi now boils down to an emotional return to Barca or a commercially driven move to Inter Miami.
Separate sources have also told ESPN that Barcelona, although determined to re-sign their greatest player ever, could not overcome "complications" to get a deal done due to the need to prove the financial feasibility of any agreement to LaLiga.
A Messi move to Miami, who parted company with coach Phil Neville last week, could represent the biggest signing ever for MLS.
Miami have reportedly held talks with Tata Martino about taking the managerial role there. Martino is a former manager for Argentina and for Barcelona, having worked with Messi on both teams.
Apple TV+ announced Tuesday that it has secured the rights to a four-part documentary about Messi's career. Apple TV+ is also in the first year of a TV rights deal with MLS.
Information from ESPN's Mark Ogden, Jeff Carlisle, Jordi Blanco and Sam Marsden was included in this report.