AC Milan have rejected a "significant offer" for Alessio Romagnoli from English Premier League Chelsea, the Italian club has confirmed.
Milan did not release financial details of the offer but it is being reported that the London club made a bid in the region of €40m.
"AC Milan has received a significant offer for its player Alessio Romagnoli from Chelsea FC," the club said in a statement on their website.
"The player is not for sale, therefore this negotiation will not continue. The club wants to thank Chelsea FC with whom we will continue to have a great working relationship."
The 21-year-old Romagnoli, who joined Milan from Roma in 2015, was a mainstay in Milan's defence last season, making 34 appearances, and is considered one of the brightest prospects in Italian football.
Chelsea manager Antonio Conte has made strengthening Chelsea's defence a priority this as Kurt Zouma's long-term knee injury has left him short of options.
Chelsea have also been linked with Napoli centre-back Kalidou Koulibaly.