United have been heavily linked with a move for the Spain international and reportedly had a €60 million bid rejected last week, with Jose Mourinho's side said to be planning a new offer.
Morata fuelled speculation he could be set to join United by 'liking' an Instagram post reporting the link on Sunday, with Juanma Lopez acknowledging the Old Trafford option is intriguing for his client.
"Manchester United? They are a club with great glamour, a very interesting option," Lopez said to CalcioMercato.com.
"I can say that their proposal is a very, very important one and now the decision rests with Real. I cannot say [if a deal will be closed soon] – we will see."
"Yes, there was frequent contact with us until a few days ago – I can confirm that," added Morata's representative.
"Quite simply, Real Madrid considered the Rossoneri's offer to be unsatisfactory."
Morata only started 14 Liga games last season, with Lopez revealing last week that his client wanted to find a situation where he would play a bigger role.