The midfielder spent last season on loan at Marseille and is understood to be keen on a return to France.
"He wants to go to Marseille and he did very well there last year, but he's got two years left of his deal here," Redknapp told talkSPORT.
"I think he's looking for the club to give him a payday here and then he'll go. I don't know how it's all going to end."
Barton joined his QPR teammates for the first day of pre-season training on Wednesday.