FIFA has ruled that Cardiff owe Nantes £5.3million for the 'first installment' of the transfer of the late striker Emiliano Sala.
However, the wording of the decision has caused considerable confusion - despite taking five days to be published - and could still be appealed.
The FIFA Players' Status Committee met last week in a bid to resolve a lengthy dispute between the two clubs surrounding the £15m transfer fee for Sala, who died in a plane crash in January shortly after being announced as Cardiff's record signing
On Monday, Cardiff were told that they owed €6million (£5.32m), which 'corresponds to the first installment currently due in accordance with the contract'.
However, Cardiff immediately sought further clarification from FIFA on the meaning of the statement, and have 10 days to decide whether or not to appeal to the Court of Arbitration for Sport (CAS).
It is unclear whether accepting the ruling would effectively set a precedent for Nantes to chase further installments. It has been reported that a second installment is due in January 2020.
Cardiff have thus far refused to make payments for the 28-year-old's transfer, saying that the deal was not legally binding because he had not signed the latest version of the contract, meaning he was not a registered Premier League player
A spokesman for Cardiff said: 'Cardiff City FC acknowledges the decision announced today by FIFA's Players Status Committee regarding the transfer of Emiliano Sala.
'We will be seeking further clarification from FIFA on the exact meaning of their statement in order to make an informed decision on our next steps.'
A FIFA statement said: 'Cardiff City FC must pay FC Nantes the sum of 6m euros, corresponding to the first installment due in accordance with the transfer agreement concluded between the parties on 19 January 2019 for the transfer of the late Emiliano Sala from FC Nantes to Cardiff City FC.
'The FIFA Players' Status Committee, which never lost sight of the specific and unique circumstances of this tragic situation during its deliberations on the dispute at stake, refrained from imposing procedural costs on the parties.
'The findings of the decision were notified to the parties concerned today.'
In response to questions by our correspondent, a further statement said: 'The sum of EUR 6,000,000 corresponds to the first installment currently due in accordance with the contract.
'For confidentiality reasons, we cannot comment at this stage on potential future installments or other conditions of the transfer agreement.'