United are supposedly looking at the Everton striker as a replacement for Robin Van Persie.
Lukaku arrived at Goodison Park last summer for a fee of £28m after a spell on loan at the club.
The Belgian notched up 20 goals in all competitions this season, and was a key figure in the Europa League for the Toffees.
Now it seems Louis Van Gaal has got his eyes on Lukaku with moves for other players looking unlikely.
It seems earlier rumoured targets Edinson Cavani, Gonzalo Higuain and Gareth Bale are most likely not to make a move over to Old Trafford this summer.
Of course, Everton will have a big price tag on the striker after forking out £28m no more than twelve months ago, but on the other hand, Van Gaal has been told by United bosses that plenty of funds are available.
Everton will be doing their best to keep hold of Lukaku, but an offer from Manchester United may become too good to refuse for both parties.