The Belgium international has been frozen out under Mauricio Pochettino in recent times after a row over a new contract.
His current deal expires in 2020 and its accepted that no agreement will be reached between the two parties.
Theres a clause in his contract that forces Spurs to sell him for just £22million next summer and Tottenham chiefs are now keen to recoup the highest fee possible for him.
And they have told United bosses that he will cost them £75m to move to Old Trafford, according to the Mirror.
While Manchester United were ready to offer £55m, Spurs chairman Daniel Levy believes he can squeeze more out of the Red Devils and he wants a figure far closer to the amount paid by Liverpool to sign Virgil van Dijk.
Negotiations are likely to be drawn out over the two parties, with Tottenham adamant they should be rewarded with a high transfer fee for a player widely regarded as one of the finest centre-backs in English football.
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