Atletico Madrid want almost £43m (€50m) if they are to sell Kieran Trippier this summer.
The Spanish champions do not want to part with the England right-back, who has two years left on his current contract.
Manchester United are interested in signing Trippier this summer to add competition for Aaron Wan-Bissaka.
However, Atletico are yet to receive an offer from United, despite reports of an approach being knocked back.
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Sky Sports News first revealed United's interest in Trippier ahead of the January transfer window but he was then banned for 10 matches for breaking FA betting rules.
The 30-year-old returned to action in March and impressed as Diego Simeone's side won La Liga over Real Madrid and Barcelona.
He is currently part of England's Euro 2020 squad and started at left-back in the opening win over Croatia.
As well as Trippier, United also have an interest in Norwich right-back Max Aarons - but the ex-Tottenham and Burnley full-back would bring a wealth of experience to Ole Gunnar Solskjaer's side.
As well as 29 caps for England, Trippier has a La Liga title under his belt and played in the Champions League final with Spurs under Mauricio Pochettino.