The Daily Record is reporting that the Red Devils have “hardened” their interest in the 20-year-old left-back as Jose Mourinho begins to think about how he will strengthen his squad this summer.
The same report says that Mourinho is planning an “overhaul” of his defence and that Tierney is being pushed as one of the Red Devils’ potential top targets this summer.
The story also claims that Celtic are likely to want a transfer fee of more than £20m for the defender if they are to sell him this summer.
The Scotland international signed a new six-year contract with Celtic last October.
He has been in good form for Celtic so far this season, scoring three goals in 27 Premiership appearances for the Scottish side.
Manchester United are likely to be linked with a host of players in the coming weeks and months as the summer transfer window gives Mourinho the chance to significantly bolster his squad at Old Trafford.
Meanwhile, the Red Devils are set to return to Premier League action on Saturday when they host Swansea at Old Trafford.
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