The Daily Star says the French champions are plotting a £40m bid for the teenage sensation this summer.
But United are determined to keep Januzaj at Old Trafford and insists he is not for sale at any price.
Under-fire boss David Moyes wants to rebuild his side around Januzaj and a club source said: “Adnan has a massive role to play in the future of the team and he can go on to become a huge success at United.
“It doesn’t matter what offers might come in for him, he will not be sold because he is not for sale.”
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