Udinese have reported Portsmouth to the Court of Arbitration for Sport (CAS) over the outstanding payments for midfielder Sulley Muntari.
The issues with that deal reportedly led to the Premier League refusing to lift the club's transfer embargo this week after two days of meetings and Portsmouth-based newspaper The News says Pompey had been looking to contact Udinese in a bid to resolve the issue.
However, this latest news could represent a major blow to any hopes of bringing in new players this month and could prove significant in the battle to rescue the club.
A Udinese spokesman said on Thursday: "I can confirm that Udinese today has reported Portsmouth to the Court of Arbitration for Sport in Lausanne in connection with a missed payment for Sulley Muntari."
Meanwhile, Portsmouth executive director Mark Jacob has vowed to fight Sol Campbell's claim he is owed £1.7 million over image rights and bonus payments.
"We are aware of it and it is being vigorously defended," Jacob said.