Milan want the forward, 27, to be available for their mid-winter training camp in Dubai in two weeks.
Vice-president Galliani is expected to arrive in England on Wednesday or Thursday in a bid to alter City's stance.
He said: "Let's hope sooner or later City change their minds.
"Negotiations are going to take a long time but we are playing a lot of emphasis on the fact he wants to play with us.
"It's true other sides are interested in him but there are not actually that many."