"Kanu hasn't got a bigger fan in the world than me," the Blues boss told Pompey's website. "He's been a fantastic footballer all his life. I could watch him play football all day - he's a master of the football.
"But, like anybody, he's not getting any younger. Every year he's signed a one-year deal and if he plays a certain amount of games, he gets another year. He'll probably still be here when I'm long gone.
"We're going to have lots of games this season - maybe 50 with the UEFA Cup.
"Every year he plays the games and he gets another year. I think that's a fair deal. You have to do deals like that with older players, because everybody gets to a stage in their life when they have to finish.
"So when players get to 30-odd years of age, you have to be very careful, but hopefully he'll play for many years to come."
Redknapp added: "Hopefully the deal will be sorted because I want to keep him at Portsmouth because I love him - he's a fantastic man and a great footballer."