Manchester United may be forced to end their pursuit of Sean Longstaff after Newcastle slapped a £50 million price tag on the midfielder, sources have told ESPN FC.

United value the 21-year-old, who has made just nine Premier League appearances, at between £18m to £20m but Newcastle are asking for more than double.

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Sources have told ESPN FC that chief negotiator Matt Judge, head of corporate development, spoke to Newcastle managing director Lee Charnley over the weekend but a formal bid was not submitted because the two clubs are so far apart.

Newcastle, according to sources, are using the £50m paid to Crystal Palace for Aaron Wan-Bissaka as a barometer for their valuation, a stance that has stunned United chiefs considering Longstaff's lack of experience.

United have prioritised the signing of Leicester defender Harry Maguire while talks are continuing with Inter Milan over the sale of Romelu Lukaku.

Manager Ole Gunnar Solskjaer wants at least one new midfielder before the transfer deadline after Marouane Fellaini departed in January and Ander Herrera joined Paris Saint-Germain at the end of the season.

If Newcastle refuse to compromise over Longstaff, who is under contract until 2022 after signing an extension in December, United are prepared to move on to other targets.

Meanwhile, Inter bosses have flown to England in a bid to negotiate a deal for Lukaku, who was absent from training in Perth on Thursday evening.

The striker has told United he is keen to move to the Serie A side despite assurances from Solskjaer that he will get opportunities next season.

Inter are keen to sign Lukaku on loan with an obligation to buy in two years but United are holding out for a fee of around £80m after paying Everton £75m two years ago.