Modric, 25, signed a six-year deal last season and insists he is happy under boss Harry Redknapp.
But loyalty comes at a price with the playmaker anxious to see how the club move forward from last season's Champions League debut.
A Tottenham insider told The Sun: "Harry's gone on record saying how Spurs won't sell Modric or any other big-name star.
"But while Luka has declared himself happy with what Tottenham have done so far, he is also fiercely ambitious.
"He's waiting to see if Harry can make a couple of 'marquee' signings. That will tell him what direction the club is heading in."