"Sunderland AFC made an offer in writing to David Bellion, which reflected his future value and potential," said a club spokesman.
"This was a much improved contract and an outstanding offer for a player of his age.
"His agent Mike Morris rejected this offer, also in writing, at the end of January. As a consequence we are now in talks with the Football League about a date for the tribunal hearing."
Bellion signed on a free transfer for Manchester Utd earlier this month but Sunderland can claim compensation because of he is only 20-year-old.