The 27-year-old, who has just 12 months remaining on his current deal at St James' Park, is eager to make the switch and has already agreed personal terms with Leeds.
Despite Longstaff's desire to join the Elland Road outfit, Newcastle are holding firm. The midfielder endured a frustrating 2024/25 campaign, failing to start a single Premier League match after January and making just 12 starts across all competitions.
Leeds have now tabled three offers this summer, the most recent submitted earlier this week.
With Newcastle unwilling to accept the 12-million-pound package, Leeds must now weigh their options - either increase their bid or turn attention elsewhere.
Hoffenheim's Anton Stach has been identified as a potential alternative. The club had previously targeted Habib Diarra and Noah Sadiki, but both opted to join Championship rivals Sunderland.
Meanwhile, Newcastle are closing in on their first signing of the summer. Anthony Elanga has completed his medical ahead of a 52-million-pound move from Nottingham Forest, with confirmation expected within 24 hours.
The former Manchester United winger will bring pace and creativity to Eddie Howe's side as they look to reshape their squad.
Newcastle United have reportedly made a bold move for Eintracht Frankfurt's Hugo Ekitike, potentially impacting Liverpool's chase for Newcastle's star striker Alexander Isak.
Newcastle United are intensifying efforts to sign a new striker, with manager Eddie Howe looking to bolster his attacking options ahead of a demanding new season.
Conor Gallagher could be on the move again, with Newcastle United emerging as strong contenders to bring the Atletico Madrid midfielder back to the Premier League in the summer of 2025.
Liverpool are reshaping their attacking line-up for the 2025/26 Premier League season, with a new centre-forward high on their priority list.
