Milan do have an option to sign the 28-year-old outright this summer for a pre-agreed 8m, but it looks like they want Catania to lower their price.
"Maxi Lopez is happy at Milan and he'd like to continue his career here," the representative told Milan News.
"The Rossoneri are satisfied with his form because they knew when they got him that he was a good player.
"However, it is not up to us now. Milan and Catania will have to strike a deal."