"I'd love to sign Appiah and we are interested in him but there's nothing going on really at the moment," Redknapp told the Portsmouth News.
"It's going to be tough to get him - there are a lot of clubs chasing him, clubs like West Ham and Arsenal, which you expect because he's a free agent.
"I am sure Juventus will want him back as well. There will be plenty of takers."
Appiah has long been on the Pompey manager's wishlist and Redknapp was gushing in his praise of the Ghana international.
"He's a terrific player for somebody on a free," added Redknapp.
"I've asked about him in the past. I watched him plenty of times when I was looking at Sulley Muntari and they played together for Ghana.
"When I enquired I was told he would cost 14 million (around £11 million).
"He's a top player but I already wanted Sulley and couldn't have both of them.
"Appiah's a fantastic footballer, he's an athlete, has a great engine, works hard and is the captain of Ghana. A lot of teams would love to sign him.
'There's a chance we might get him, like I say, we are interested in him. We'll just have to see what happens.
"But there is a lot of competition out there which you expect for a very, very good player like that."