The Belgium international is likely to be sold ahead of next season, and Standard Sport are also reporting that the money gained from his sale will be used to lure Ajax ace Matthijs de Ligt, whose reputation has soared over the past few months.
Alderweireld rejected Spurs' last offer earlier this year, and the probability of the club meeting his £120,000-a-week demands - more than double the £50,000 he earns at the moment - is thought to be very low.
United are understood to be ready to splash £40m to secure a deal for the 29-year-old and are willing to pay him a lot more than what Spurs last offered. They are also prepared to hand him a multi-year deal that will see him remain under contract until his mid-thirties, as opposed to Tottenham, who have so far refused to commit to a lengthy period, given the player's age.
Toby Alderweireld is the best centre back in the Premier League and would be a sensational signing for Manchester United. Won't be easy, but well worth it if there's a chance to recruit him.— Liam Canning (@LiamPaulCanning) May 15, 2018
The Red Devils aren't the only interested party, however, with Chelsea, Paris Saint-Germain and Barcelona all believed to be monitoring the situation.
Mauricio Pochettino had previously suggested that the club would hold more talks with Alderweireld in a last-ditch attempt to get him to stay, yet the player is said to have already left for holiday in Greece and no negotiations have been scheduled.
Meanwhile, the 18-year-old De Ligt, who has already made five appearances for the Netherlands after breaking out last season, is valued at £50m. Spurs are notorious for avoiding such sums, but selling Alderweireld will make it so they're hardly bothered.