Barcelona are to report Manchester United to FIFA after the English premier league side said it had signed teenage defender Gerard Pique, the Primera Liga club says.
Barcelona say United, who announced their new signing on Thursday, have breached the Spanish Primera Liga club's rights over the 17-year-old, a product of their youth academy over the past seven years.
FIFA have said clubs that train up young players have the right to compensation payments if they move to other teams.
"We have sent a request to the Spanish Football Federation to ask them to put our case to FIFA and the English Football Association," Barcelona president Joan Laporta told the club's website.
He told Barcelona-based daily El Mundo Deportivo: "Manchester have acted in a belligerent manner in this case and have failed to respect the effort that some clubs are making in bringing on young players.
"We are going to see this case through right to the end."
Pique, a Spanish under-17 international and grandson of former Barcelona director Amador Bernabeu, said he was free to join United.
"You can see that Barca don't want to negotiate," El Mundo Deportivo quoted him as saying to Radio Catalunya.
"They say I belong to them, but I'm not a slave. If they don't want to negotiate then FIFA will have to decide what United have to pay."