Newcastle have rejected a bid of £20m, rising to £25m from West Ham for captain Jamaal Lascelles, Sky Sports News understands.
One source told Sky Sports News on Tuesday morning that the player is not for sale.
The 24-year-old, who is also the subject of interest from Everton, reported back for pre-season training at Newcastle on Friday.
Lascelles made 33 Premier League appearances for Newcastle last season, scoring three times.
West Ham boss Manuel Pellegrini has already secured the signings of midfielder Jack Wilshere, centre-back Issa Diop, goalkeeper Lukasz Fabianski and full-back Ryan Fredericks.
Sky Sports News reported on Monday that the Hammers are in advanced talks with Lazio over the signing of winger Felipe Anderson.
It is understood the clubs are edging closer to an agreement on a fee, the payment structure and potential clauses after negotiations had stalled over the past couple of weeks.
Anderson, according to Sky sources, would become the club's record-transfer - exceeding the £21.9m fee they paid French side Toulouse for Diop earlier this summer.