Sporting CP have pulled out of a deal to sign Kevin Prince-Boateng following a disagreement about the Ghana international's image rights, the Portuguese club announced on Wednesday.

Sporting said that "after negotiations with Kevin-Prince Boateng, it was not possible to reach an agreement relating to his image rights."

A few hours earlier, Portuguese media reported that the deal had hit a stumbling block because Boateng had failed a medical.

The 28-year-old, who was born in Germany and has spent the last two seasons at Schalke 04, had appeared set to sign a two-year contract at the Estadio Jose Alvalade, according to local press reports.

The former Hertha Berlin, Borussia Dortmund, Portsmouth and AC Milan forward was suspended indefinitely by Schalke in May after the Gelsenkirchen club's Bundesliga defeat to Cologne.