Manchester United are interested in making Longstaff their third young, British signing of the summer.
The club have already picked up Daniel James and Aaron Wan-Bissaka from Swansea and Crystal Palace, respectively.
Manager Ole Gunnar Solskjaer wants to overhaul his ageing United squad with young players who are willing to commit themselves to the club.
And the Norwegian sees Longstaff as one of those players.
United believe they can wrangle Longstaff away from St James’ Park for £25m but Newcastle have rebuffed initial approached from the Red Devils.
The midfielder came into the staring XI at Newcastle midway through last season and impressed before picking up a knee injury against West Ham.
And according to the Mirror, Longstaff is willing to accept that Newcastle, who want closer to £50m from United, are going to price executive vice-chairman Ed Woodward out of a move.
Longstaff is keen on moving to United but is fully committed with staying at his boyhood club Newcastle.
Solskjaer is looking for midfielder reinforcements after the departure of Ander Herrera and with Paul Pogba’s future at the club up in the air.
Longstaff would suit Solskjaer’s plans, as would Sporting Lisbon’s Bruno Fernandes.
Fernandes is also being linked with a move to Old Trafford after his brilliant season in Portugal.
The midfielder scored 20 goals and registered 13 assists last season in the league for Sporting.
Pogba, meanwhile, has hinted that he wants to move to dream club Real Madrid in search of a fresh challenge.
“I have been three years in Manchester and have been doing great – some good moments and some bad moments, like everybody, like everywhere else,” he said.
“After this season and everything that happened, with my season being my best season … it could be a good time to have a new challenge somewhere else.”