Manchester United have reportedly been informed by Napoli that Kalidou Koulibaly will cost £110m.
The Red Devils are also thought to be after a new centre-back ahead of the 2019-2020 campaign, and Koulibaly has been linked with a switch to Old Trafford over the last few months.
The 20-time English champions are believed to have placed a £90m bid on the table, but according to The Express, Napoli will not sell the Senegal international for under his £110m release clause.
The 27-year-old has made over 200 appearances for Napoli since a 2014 switch from Genk, developing into one of the best central defenders in the world over the last few seasons.
Tottenham Hotspur's Toby Alderweireld and Inter Milan's Milan Skriniar are also said to be under consideration by Ole Gunnar Solskjaer's side ahead of this summer's transfer window.