The contract of the teenage sensation at the Principality expires in 2021, but his representatives are in a legal dispute with the club and want the contract broken.
This will enable Mejbri leave for free, and it seems he will be moving to Old Trafford.
He already handed in a transfer request in January in order to force a move, and the likes of Arsenal, Liverpool, Barcelona and Lyon who had all earlier approached his representatives for a deal are now set to miss out on his signature.
Mejbri left Paris FC for Monaco in 2018 and is widely regarded as one of the brightest talents in France.
Although the midfielder is yet to make his first team bow, he has impressed the club’s coaches with his rapid development, and the Ligue 1 side aren’t keen on letting him go.
United manager Ole Gunnar Solskjaer has handed youth duo Tahith Chong and Mason Greenwood playing chances this term, and Mejbri will fancy his chances of breaking into the first-team soon enough if a summer move works out.