Sheffield United's lawyers insist the Court of Arbitration for Sport has no right to intervene in their claim against West Ham.
The Blades hope to win a reported £50million in compensation from the London club after an independent tribunal recently judged in their favour in the Carlos Tevez affair. But West Ham want the Yorkshire club's landmark legal victory overturned and have appealed to CAS, who have given the Blades a 24-hour deadline to respond to the Hammers' submission.
Sheffield United will argue CAS does not have the power to overturn the judgement and that West Ham agreed to the arbitration being binding, waiving their rights to appeal, but the Londoners are relying on FIFA rules which allows the decisions of national football associations to be appealed to CAS.
A three-man Premier League arbitration panel fined the Hammers £5.5million last April, but did not dock them points, for acting improperly and withholding vital documentation over the ownership of Argentine duo Tevez and Javier Mascherano in 2006.
West Ham escaped relegation on the final day of the 2006/7 season - Tevez scored the winning goal at Old Trafford - while the Blades lost at home to Wigan and went down.
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