Spurs have spent much of the summer trying to keep their Croatian playmaker out of the clutches of a Premier League rival.
Chelsea have led the chase for Modric, tabling big-money bids, but Manchester United and Manchester City are also believed to be keen.
Redknapp understands that a player of such ability is always going to attract interest, as he considers Modric to be good enough to represent Barcelona, but insists there is no point in parting with that quality when a top-four club comes calling.
Instead, he wants Spurs to put down a marker in the transfer market and prove to Modric that the future is bright at White Hart Lane.
"I can understand how Luka feels in all this," said Redknapp. "If anyone offers to treble your wages you'd be interested and Chelsea are a big club.
"Everyone wants Luka. Just ask Alex Ferguson what he thinks of him, ask Roberto Mancini at Manchester City - they all want him. He could play for Barcelona.
"Luka wants the chance to win things and he is ambitious. All I'll say is that we are too at Tottenham.
"It's early days in the transfer market and no-one is more ambitious than our chairman Daniel Levy.
"Luka wants to know that we'll be right up there challenging next season and we are working hard to bring in a couple of big signings that may convince him to stick with us. I hope so.
"I have sympathy for Luka and his character has shone through in all this.
"He's a fantastic bloke and a genius of a player. I'd just ask him to be patient."
Source: Team Talk
Source: Team Talk