The Ivory Coast international has been involved in a tug-of-war in recent times with Wolves and Blackburn both jockeying for his services as Pompey deal with financial uncertainty and the Championship.
"My agent informed me about a contact from Panathinaikos. I don't know how serious the interest of the club is, but I told him to proceed because I'm really interested," he said.
"It's obvious I would choose Panathinaikos, who will participate in the Champions League and constantly fight for the league title in Greece.
"That's something very difficult to achieve at other clubs besides the top four in England and it's something that really excites me.