Milan reportedly want €15m for Mattia De Sciglio, whereas Juventus are only offering €10m for the full-back.
The 24-year-old will be out of contract in June 2018 and is refusing to sign a new deal.
His rapport with the fans has been increasingly tense and he is regularly jeered when playing at San Siro.
According to Tuttosport, the Rossoneri have set a €15m price-tag on the Italy international, but Juventus are so far offering €10m.
De Sciglio came up through the Milan youth academy and was launched into the first team by Max Allegri, who is eager for a reunion.
He has 31 senior caps for Italy and is prized for his versatility, able to play on the right or left side of defence, plus in a more advanced role.