The 68-cap Senegal international is rated as one of the top defenders in Ligue 1, having twice made it into the division’s Team of the Year since moving to Stade Velodrome in summer 2011.
The 6 foot 1 centre-back is set to leave the French club when his contract expires at the end of the month however, meaning he’ll be available on a free transfer.
La Liga outfit Espanyol remain the front-runners in he race to sign N’Koulou, having seemingly agreed terms with the former Monaco man some time ago.
But it appears West Ham are looking to throw a late spanner in the works, with L’Esportiu claiming the east Londoners tabled a contract offer on Saturday.
However, Espanyol still remain confident of pushing through a deal after appointing former Watford boss Quique Sanchez Flores as their new manager earlier this month.