"We are saddened that our association with a player has been soured by what we believe is a financially-motivated action," said West Ham secretary Scott Duxbury in a statement.
"To date, no proceedings have been formally served so we are unable to comment on specific allegations.
"However, from the details that we have so far been given the club believes this action to be wholly without merit and we will vigorously defend any proceedings that are ultimately served."