In two years at Old Trafford, Miller has made only 22 first-team appearances and despite many senior players missing, he was still only a substitute in the opening game of their current tour of South Africa on Saturday.
The 25-year-old spent the latter half of last season on loan at Leeds, as he helped the Whites into the Championship play-off final.
But Leeds' failure to beat Watford at the Millennium Stadium spoiled any chance of Miller making a permanent move to Elland Road.
But Sir Alex Ferguson has accepted it would be better for all parties if Miller did move on and hopes a deal can be sorted out prior to the August transfer deadline.