Mainoo, 20, had previously requested a loan move in the summer, but the club declined his request.

Zirkzee, 24, has also expressed dissatisfaction with his lack of playing time and was reportedly seeking a transfer, with West Ham mentioned as a possible destination.

According to club sources, United will not consider releasing either player in January, even if other clubs make offers.

The club's decision is partly driven by the upcoming Africa Cup of Nations, which will take place in January and could see several players leave for the tournament.

This will result in the club being without those players for at least six domestic fixtures, and they want to keep their squad intact during this period.