Cardiff City have been placed under a transfer embargo after failing to pay the first instalment of the fee owed to Ligue 1 club Nantes for Emiliano Sala, the Championship side confirmed to the BBC on Saturday.
Sala died in a plane crash in the English Channel as he travelled to Cardiff after signing for £15 million ($18.21m) in January 2019. The pilot of the flight, David Ibbotson, also died.
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Cardiff had appealed against a FIFA decision ordering them to pay the first instalment of his transfer fee, which amounted to €6m ($6.35m).
The Court of Arbitration for Sport (CAS) ruled in August that Cardiff had to pay Nantes the first instalment. The Welsh club appealed the CAS decision to a Swiss Federal Court, with a verdict expected next year.
Cardiff said they are also talking to the English Football League and football's global body FIFA to resolve the issue.
The Championship club's chairman Mehmet Dalman said he was confident that they would be able to lift the embargo before the transfer window reopens in January.
"I wish I had the power to lift the shadow of this situation from the club. People at this club want this resolved," Dalman told the BBC.
"People should not forget that a ... man was killed when there was no need for that accident to happen. There is a human side to this story, it is not just a financial one."
Dalman said there were "lots of legal discussions" going on and that the club had received their first invoice from Nantes.
"We haven't paid it and at this stage have no intention of paying it until certain negotiations come to fruition," he said.
Cardiff are 20th in the Championship after 23 games.