Atletico Madrid have asked La Liga to block French forward Antoine Griezmann's move to Barcelona in a dispute over the transfer fee between the two clubs, according to the Spanish league's president Javier Tebas.
Spanish champions Barcelona announced the signing of Griezmann this month for €120 million ($133.75m) but Atletico complained that the Catalan club had not paid enough to trigger the player's release clause.
The buy-out clause had dropped from €200m to €120m on July 1, but Atletico claim that Griezmann's May 14 announcement that he was leaving the club is proof a deal was struck between the player and Barcelona much earlier.
"[Atletico] submitted a complaint and put in doubt whether we should pass Griezmann's licence to Barcelona," Tebas told Spanish radio station Onda Cero on Wednesday.
"There's a process that has been put in motion and those overseeing it will have to come to resolve the case.
"It is possible to block a player's transfer. La Liga will have to decide what course of action to take."
Griezmann has already played a friendly for his new club, a 2-1 defeat by Chelsea in Japan on Tuesday.