Premier League champions Manchester City are also eyeing the 21-year-old midfielder.
It comes as Real Madrid have sent scouts to watch Wharton since his return to Crystal Palace's first team.
Juni Calafat, the Spanish club's chief scout, is known to be a big admirer of the 21-year-old England international.
Wharton, who is likely to be included in Thomas Tuchel's first England squad, recently made his comeback following a lengthy spell on the sidelines whilst recovering from hernia surgery.
Manchester City had been expected to move for him in January, but the timing of his injury saw them turn their attention elsewhere, ultimately signing Nico Gonzalez from Porto instead.
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Both Manchester United and Liverpool rate Wharton highly, though their transfer focus lies elsewhere heading into the summer window.
Palace secured Wharton from Blackburn Rovers in a deal worth £22million after sporting director Dougie Freedman pushed to beat other Premier League clubs to his signature.
Having advanced through the academy at Blackburn, Wharton made his senior debut in August 2022 and has continued to impress for the Eagles.
Wharton has since developed into one of the league's standout holding midfielders, his market value has now soared to around £70 million.
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Coach Oliver Glasner has carefully managed Wharton's return throughout February, and the midfielder delivered a man-of-the-match display in his first start back.
That started ended in a 4-1 win over Aston Villa, watched closely by Tuchel at Selhurst Park.
Wharton was called-up to England's Euro 2024 squad and made his debut in a friendly with Bosnia last June.
With Madrid still weighing their options for the summer, they will continue to track his progress.
Liverpool's Trent Alexander-Arnold is also on Madrid's radar, though the club prefer to do their transfer business with out-of-contract stars.
Last summer, Wharton was targetted by Bayern Munich, though ended up staying at the south London side.
Instead, the Bundesliga side opted for Michael Olise who joined the German giants for a fee worth £60million.
Palace, who take on London rivals Fulham in the FA Cup quarter-finals, are preparing for a wave of interest in their key players, with Eberechi Eze, Marc Guehi, and Jean-Philippe Mateta also on the radar of top clubs.
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