Neither defender has been offered a new contract by the London-based club.
Per The Standard, manager David Moyes' future is playing a role in the delay.
The club want to ensure that they know who is in charge next season before making decisions about players.
No final decision has yet been made over the Scot's future, given rumors that West Ham have been speaking to other coaches.
The likes of Ruben Amorim from Sporting CP and Lille manager Paulo Fonseca are targets.