But United might be left with no choice but to sell Lukaku for less than their asking price because the forward's situation has now become untenable.
In the meantime, Lukaku has remained in Belgium, where he has been training with Anderlecht and is refusing to return to Manchester.
The Independent has since reported that it was the Red Devils' day off and that Lukaku had been given permission to train with the Belgian side.
The window for Italian clubs to register doesn't close until September 2, giving Inter more than three weeks to finalise a deal with United regarding the purchase of Lukaku.
The 26-year-old has missed United's ideal winning run during pre-season owing to a foot injury, but Ole Gunnar Solskjaer has been open to the idea of selling the striker this summer as part of his squad rebuild at Old Trafford.
PA understands a move to Serie A remains on the cards, eyebrows were raised on Monday when the striker was pictured training with boyhood club Anderlecht.
However, sources have told ESPN FC that Luke Shaw, who was bottom of the list, was among those unhappy the information had been made public prompting Solskjaer to rebuke the Belgium worldwide.
Inter and Juventus feel if the Premier League side can replace Lukaku with Llorente, they will still be willing to deal after Thursday. Smalling has fallen down the pecking order following the arrival of £80m centre-back Harry Maguire from Leicester but Solskjaer wants to keep him at Old Trafford.
Two years after arriving at Old Trafford in a big-money switch from Everton, the 26-year-old is hoping to move on to pastures new. Smalling is one of seven central defenders in Solskjaer's squad, which also includes Maguire, Victor Lindelof, Phil Jones, Eric Bailly, Marcos Rojo and Axel Tuanzebe.