According to the Guardian, the Italian club will offer an initial two-year loan deal worth €10m with an obligation to buy the forward for €60m at the end of the loan period.
The club met with the 26-year-old's representatives on Wednesday, reiterating his desire to play in Serie A.
Lukaku has spent two seasons at Old Trafford, making 96 appearances and scoring 42 goals, but he lost his place under Ole Gunnar Solksjaer towards the end of last season.
A swap deal was apparently proposed earlier in negotiations but reports now suggest that is not an option.
Inter are yet to meet Manchester United, though meetings are thought to be in the offing early next week.
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