Montgomery, 24 has been at Bramall lane throughout his professional playing career since he was let down by Leeds United; but has been in and out of the side this season since the arrival of Mikele Leigertwood.
The Midfielder started and captained the Blades 3-0 defeat at home to Swansea City in the FA Cup admit fears that he could soon leave; and a very decent offer from the Hammers could trigger a transfer.
It is expected, if a deal is done that West Ham United will pay £1,500,000.