Kharja played on-loan with Inter Milan for part of last season.
It's understood that the two clubs have agreed a 3m co-ownership deal in principle, with personal terms now set to be discussed.
"He is close," Beppe Galli told Firenze Viola. "I know that an agreement between the two clubs has basically been agreed, even if I don't know about the details.
"Now I need to speak with the Viola, something which I think will occur during the next few days," he added.
"I can say that Houssine would be very happy to join Fiorentina, it's a fantastic destination. We're hopeful it will be done."
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