Lionel Messi's father has written to La Liga insisting the player is contractually allowed to leave Barcelona for free in the current transfer window.
The league had stated last weekend that it believed a buyout clause of €700 million still applied, but Jorge Messi - who also acts as the player's agent - insists the player's contract allowed him to exercise an option to leave at the end of the 2019-20 season.
In the letter sent on Friday, which has been seen by the PA news agency, Messi senior argues that his son's contract does not specify a date when the option to leave must be exercised, simply that it must be done at the end of the campaign.
Barca's season ended on 14 August when they were hammered by Bayern Munich in the Champions League quarter-finals.
Messi's representatives sent a fax to the club on 25 August expressing his desire to leave.
LaLiga agreed with Barcelona that the buyout clause was still applicable in its statement on the matter last Sunday, and it is understood it will address the content of Jorge Messi's letter later on Friday afternoon.
Last Sunday a league statement read: "In compliance with the applicable regulations, and following the corresponding procedure in these cases, LaLiga will not carry out the prior visa process for the player to be removed from the federation if they have not previously paid the amount of said clause."
Messi, who has been with the Catalan club since the age of 13, did not arrive for a scheduled club coronavirus test last Sunday morning.
Since news of Messi's desire to leave became public, a handful of the world's richest clubs have been linked with him, including Manchester City, whose manager Pep Guardiola was his boss at Barca between 2008 and 2012.
It has been reported that he is unhappy with the direction of the club under its current president Josep Bartomeu.
Meanwhile, Messi's close friend and team-mate Luis Suarez is set to join Serie A giants Juventus on a free transfer.
According to BBC Radio 5 Live's Guillem Balague, the Uruguayan, who has one year remaining on his Barca contract with an option for an additional year based on games played, will leave the Catalan club provided he can negotiate a release.
Balague suggests the former Liverpool, striker's departure "has no bearing" on Messi's future and that Suarez would accept to be paid off with the equivalent of one season's wages in order to pave the way for a move away.