The Portugal midfielder, who is also being monitored by Chelsea, is being lined up for a move to the San Siro, with Inter agreeing a £33.4million fee with Sporting Lisbon.
Jose Mourinho is still looking to build his new Manchester United team, and was reportedly keen on the fellow Portuguese star being part of his revolution at Old Trafford.
Joao Mario was United’s back up plan, after missing out on his countryman and EURO 2016-winning teammate Renato Sanches, who moved to Bayern Munich at the start of the summer.
Chelsea had also been linked with the midfielder, who’s agent Kia Joorabchian has links to the Blues, helping bring Matt Miazga and Alexandre Pato to Stamford Bridge back in January.
Inter Milan are under new ownership after being taken over this summer, and are keen to spend money to rival Juventus at the top of Serie A.