United have held talks with Newcastle over a deal for the 21-year-old and are willing to submit a £20 million offer.
But United were left stunned as Newcastle demanded in excess of £50m for the midfielder.
According to The Times, Longstaff would be keen on a switch to United but fears Newcastles high valuation will scupper any potential deal.
The report claims that United are unwilling to meet the price tag set by Newcastles managing director Lee Charnley.
Longstaff has made just nine Premier League appearances for Newcastle while his breakthrough season was cut short in March after he suffered a knee ligament injury.
The 21-year-old is currently in pre-season training with Newcastle, who remain without Read More – Source