Manager impressed by wingers form so far
Routledge, who has been on a loan spell at Loftus Road from Newcastle United, has made a great impact at the club, scoring two goals in his last eight appearances.
Warnock has been impressed by the winger's form of late and is hoping to secure a permanent deal for the 26-year-old.
"I think they've sorted out a realistic figure," Warnock told the Fulham Chronicle.
"I can't give exact details, but I think we've agreed everything with the club should it go ahead.
"I don't think there's any rush for either of us. We'd like to sign him, whatever happens, but I imagine it depends on where we end up, because I think Wayne would like to play in the Premier League. If things went wrong for us, then he'd probably go back.
"He's got to be enjoying it because of the way he's playing and we're enjoying having him. We'd love to keep him."
Warnock added: "I thought he'd do well for us. That's why I chased him for so long and talked to him so many times. Pestered him, in fact.
"It can sometimes be difficult coming back to a club, but I told him it was a lot different now and I felt the club was geared up to let him play his best.
"I thought we were a solid side and I thought you need players like Wayne to win games and I'm delighted to get him."