Napoli are edging towards agreeing a new contract with Everton and Manchester United target Dries Mertens, but a potential release clause is causing issues.
The Belgium winger's contract with the Serie A side expires in 2018 and he has been linked with a number of sides, not least in the Premier League.
Napoli are desperate to keep hold of Mertens and on Sunday the club's president Aurelio De Laurentiis met the player's agents to hold further contract talks.
A three-year deal worth €3m per year is on the table, but the main problem now is a release clause, according to Italian daily Il Messaggero.
Mertens' agents, who are also aware there client has serious interest from China, want a release clause of between €25m and €30m, which would allow their client to move on at some point without Napoli being able to prevent his departure.
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The winger has been in superb form for Napoli in the current campaign and the Serie A side want to keep him at the San Paolo.
Mertens has scored 27 goals in 40 appearances this season.
