United, Manchester City and Blackburn Rovers have been alerted to his position, which has been brought about purely by the length of Everton's contract offer and not the financial terms. They are only offering a further 12 months.
The defender could be tempted away if Leeds, Manchester City or Blackburn Rovers offer the three-year contract he was seeking from his boyhood club.
But Everton hope a revised two-year contract would allow a compromise deal to be reached instead.