Tottenham defender has a clause in his contract which expires in 2019.
Alderweireld is able to leave for just 28 million Euros next summer, increasing the onus on Spurs to cash in while they can.
HLN report there is some question over the legality of the agreement, and that Tottenham themselves question how valid it is.
Alderweireld could take his case to the Court of Arbitration for Sport to ensure he gets his way, it is reported.
Spurs, the report states, are keen on selling Alderweireld this summer but only for above 50 million Euros.
Tottenham really would rather it not get to next summer, to avoid the unwanted issue of Alderweireld’s release clause causing further friction.
It would be humiliating for Spurs to have to sell the Belgian for a cut-price fee, while a legal battle could get ugly, and would not be in the interest of player or club.
A middle ground must be found with buyers over Alderweireld’s future this summer before the transfer window closes.
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