A proposed move to Old Trafford for Spanish striker Morata has been ever present since the domestic season in England and Spain finished late May.
United boss Jose Mourinho is keen to add the former Juventus goalscorer to his squad for next season with terms between the Premier League club and the striker having been agreed.
However, a transfer fee is yet to be agreed between United and Madrid, following another rejected offer of £70.2m.
Goal.com report that the offer was snubbed by Real and that they are holding out for an extra £10m on top of that figure.
The report also claims that the Spanish international does not want to re-join Madrid for their pre-season training next week and will contact the Spanish capital side to force through a move.
Morata, who began his career with Madrid left the club in 2014 for a two-year spell in Italy. He later returned to Madrid and helped Los Blancos to a La Liga and Champions League title last season.
The 24-year-old scored an impressive 20 goals for Madrid last season, despite playing regularly from the substitutes bench.
Source: La Liga News