The Daily Mail says Lukaku has returned to light training as he races to be fit for the Manchester derby at the Etihad on Sunday.
Lukaku picked up hamstring injury a week ago and missed the wins over Juve and Bournemouth. United's £75million striker had already paid the price for scoring just four goals in 14 appearances this season after he was dropped to the bench by Jose Mourinho for the win over Everton.
But Mourinho wants Lukaku's power against Manchester City in this weekend's Etihad derby and will wait to see if the big Belgian can prove his fitness over the next 24 hours. He will give an update on the striker's progress on Friday lunchtime.