Contract talks between Napoli and their ​Polish midfielder Piotr Zielinski have stalled due to a disagreement over his release clause, according to reports from Italy.

Zielinski is under contract at the Stadio San Paolo for another three years but the release clause of £57m (€65m) which was included when he signed for the club in 2016 looks worryingly low in the current market.

VfL Wolfsburg v SSC Napoli - Pre Season Friendly Match

​Napoli president Aurelio de Laurentiis wants to double the release clause to £114m (€130m) but both Zielinski and his agent feel that this is excessive, ​Calciomercato understands.

If a contract extension cannot be agreed, then Zielinski's current release clause leaves Napoli in a vulnerable position, with ​Juventus and ​Liverpool both said to be eyeing a move for the 24-year-old.

Liverpool were linked with Zielinski when he was on loan at Empoli from Udinese in 2016. Empoli president Fabrizio Corsi claimed earlier this week that ​the Reds wanted Zielinski but he rejected them in favour of a move to Naples.

"When he came to Naples, he had that option [to go to Liverpool], but they did really well to convince him," explained Corsi.

Zielinski has made 104 appearances for Napoli since joining them two years ago and was a regular last season as I Partenopei recorded their highest ever Serie A points tally, although they still missed out on the title to Juventus.

He is currently away on international duty with Poland and played the full 90 minutes of the 3-2 defeat to Portugal on Thursday.