The midfielder was identified as a primary summer target by OIe Gunnar Solskjaer.
And Starsport reported earlier this month how the manager wanted Longstaff signed in time to fly out with the squad to Australia.
But United ultimately departed for Down Under without the Geordie ace, who impressed the Red Devils in his breakthrough season.
Injury disrupted the 21-year-old’s campaign although he caught the eye enough during the winter period.
Longstaff is now back fit following a knee problem and is training with the Newcastle squad in pre-season.
His future is still up in the air while Newcastle focus on appointing their new manager before turning attention to signings and outgoings.
Ex-Sunderland boss and current Sheffield Wednesday manager Steve Bruce is now poised to be confirmed as Rafa Benitez’s successor as soon as tomorrow.
And while Bruce is set to arrive on Tyneside, it seems Longstaff is close to exiting.
“Longstaff is not the only midfielder on United’s agenda”
According to The Guardian, Newcastle are ‘on the verge’ of parting with Longstaff to United.
Talks have been held between the two clubs over the past fortnight.
And it appears progress has been made in negotiations as Solskjaer looks to bolster his midfield options.
Longstaff is not the only midfielder on United’s agenda, with Sporting’s Bruno Fernandes and Lazio’s Sergej Milinkovic-Savic also wanted.
In terms of their role in the team, though, Longstaff is more defensive natured and is viewed as the long-term replacement for fellow Geordie Michael Carrick.
Reports have suggested Newcastle have been holding out for closer to £50m for their top prospect.
Initially it was believed United would be able to strike a deal for nearer the £25m to £30m bracket.
While The Guardian do not outline a fee for Longstaff, it could be a matter of time before we see the Newcastle man wearing red.
Manchester United have largely been left frustrated in their pursuits of midfielders this summer with Sporting holding firm over their £50m-plus valuation of Fernandes.
But bringing in Longstaff would help ease the situation, especially with Paul Pogba openly pushing for a move to either Juventus or Real Madrid.