The 20-year-old pushed for a temporary move away from Old Trafford in the last few days of the summer transfer window, but his requested was turned down by United.
Mainoo has fallen down the pecking order since Ruben Amorim took charge, with the struggling manager unable to find a place for him in his 3-4-3 system.
Now, according to The Daily Star, the midfielder will once again push for a loan move in January in a bid to keep his 2026 World Cup hopes alive.
England boss Thomas Tuchel has left him out of all of his England squads so far, citing that he needs more game time.
Mainoo has just two years remaining on his contract at Man United, with worries over game time a major stumbling block in negotiations.
