Mauricio Pochettino is resigned to losing the former Southampton and Atletico Madrid defender, but Spurs believe Liverpools world record purchase of Virgil van Dijk in January has changed the goalposts.
Jurgen Klopp sanctioned the £75m signing of Van Dijk and Spurs are adamant Alderweireld should command a similar fee.
The Belgium internationals situation has been further complicated by a clause in his current contract which states he can be sold for just £35m next summer unless he signs a new deal before then.
Jose Mourinho and Ed Woodward have made an impressive start to their summer transfer dealings, completing the signings of Brazil international midfielder Fred and highly-rated Portuguese right-back Diogo Dalot for a combined total of over £70m this week.
If United fail to agree a deal with Spurs for Alderweireld, Mourinho is likely to switch his attentions elsewhere.
Reports on Thursday claimed United had already made an approach for Clement Lenglet, while Mourinho is also said to be an admirer of Real Madrids Raphael Varane and Bayern Munichs Jerome Boateng.
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