The 32-year-old defender's current deal is set to expire at the end of the season.
The club had turned down offers for Maguire during the summer, with manager Ruben Amorim insisting on keeping him.
Amorim also triggered a one-year extension in Maguire's contract in January.
United is now preparing to offer Maguire a new contract, but on reduced terms from his current £190,000-a-week salary.
