The Belgium international wants to leave Old Trafford as Ole Gunnar Solskjaer views Marcus Rashford as his first-choice striker for the new season.
Antonio Conte is desperate for Inter to sign Lukaku and the Italian club have held talks with United this week.
But United are refusing to let Lukaku leave on the cheap and the Daily Telegraph claim that they want at least £90m before they allow the forward to leave.
The report claims that Inter had initially proposed a two-year loan deal where they would pay £9m up front plus a further £53.7m fee to sign the Belgian permanently.
But United are not interested in a loan deal, nor are they willing to entertain Inters efforts to include players as part of an exchange deal.
The Serie A club are looking to offload Radja Nainggolan and Mauro Icardi and while both have been offered to United, Ed Woodward has not shown any indication that he wants either player at Old Trafford.