The Italian club are still owed around £3million following their sale of Sulley Muntari to Pompey in summer 2007.
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The Ghana international has since moved back to Italy with Internazionale in a deal which earned the Fratton Park club a fee in excess of £12million.
However, Udinese remain out of pocket and have asked CAS to rule on the matter.
Portsmouth are currently under a transfer embargo despite the latest round of television revenue money being used by the Premier League to pay off other football creditors.
Pompey have hit out at the league after the £7million was used to pay off outstanding transfer fees owed to other English clubs.
Meanwhile, they have also been threatened with a winding-up order from HM Revenue and Customs over unpaid tax.
Source: DSG
