The Belgian centre-half's contract runs out in 2020 but has a clause that will allow him to leave for £25m in summer 2019 if no new deal is agreed.
There is currently an impasse in negotiations, and initial hopes that the 28-year-old would agree to a new deal have receded of late, with a considerable difference in position on wages.
Sources close to the situation maintain that Alderweireld's representatives see Virgil van Dijk's deal with Liverpool as setting a new baseline for top defenders, and that they would want a deal closer to his reported wage of £180,000 a week.
The ongoing inability to strike a deal has piqued Barcelona's interest, and they are willing to make an offer in the summer if no new contract is agreed.
Spurs' position will be weakened, given that they would have to sell for £25m in 2019.
Manchester United also have an interest in Alderweireld, but there is understood to be a reluctance at the Old Trafford club to deal with Daniel Levy.
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