Sean Longstaff has made nine appearances for Newcastle this season

Manchester United are interested in signing Newcastle's young midfielder Sean Longstaff, Sky Sports News understands.

Ole Gunnar Solskjaer is keen on adding young, home-grown talent during the summer transfer window as he looks to rebuild the squad.

Newcastle say they have had no approach from United and that 21-year-old Longstaff is not for sale.

Longstaff signed a new contract at St James' Park in December that runs until 2022, but Sky Sports News understands that was to reward him for first breaking through into the first team.

Rafael Benitez has predicted a big future for Longstaff

Now that he has become a more regular feature under Rafael Benitez, there are expected to be discussions over another new deal this summer, which would bring him more in line with the salaries of other first team members.

Longstaff made nine appearances during his debut season in the Premier League, but it was cut short after the central midfielder suffered a knee ligament injury during Newcastle's defeat to West Ham.

The young prospect, who came through the club's academy system, scored on his debut in a 2-0 victory against Burnley in February.

Longstaff signed a new contract with Newcastle in December

Benitez has previously tipped the South Shields-born midfielder to have a big England future.

Longstaff also earned praise from Pep Guardiola after the Magpies' famous 2-1 win against Premier League champions Manchester City, one of only four defeats they suffered during the 2018/19 season.

Sky Sports News reported earlier this month that United are close to agreeing a £15m deal with Swansea City for their young winger Daniel James.

United's activity in the transfer market could be extensive this summer with executive vice-chairman Ed Woodward pledging to help Solskjaer rebuild the squad following a "turbulent" season.