The Rossoneri have made a ??17.5m (???25m)??bid to acquire the 20-year-old centre-back, who is under contract with Roma until June 2018 and has also been linked with Arsenal.
Roma have reportedly told Milan they must increase their offer by a further ???5m to have any chance of signing the Italy Under-21 international, but Galliani says that will not happen.
“Our offer for Romagnoli is unchangeable,” Galliani said to Gazzetta dello Sport. “Romagnoli is an interesting player and if we can, we will satisfy our coach.
“Otherwise, we will look at other alternatives.”
AC Milan appointed former Sampdoria coach Sinisa Mihajlovic as their new manager last month.
Mihajlovic is an admirer of Romagnoli, who he coached last season when the defender was on loan at Sampdoria.