Olympique Marseille and Watford are set to battle over the registration of Pape Gueye.
Reports of the two clubs settling on a compensation fee for the midfielder now appear wide of the mark.
Gueye, while with Le Havre, signed a pre-contract with Watford earlier this season - though has sought to pull out of the deal.
He has since agreed terms with OM, but the Hornets are unhappy with the situation.
La Provence says Watford are now prepared to take the matter to FIFA, having written to OM to warn them of consequences over their agreement with Gueye.
