According to the sources, United have agreed to a world-record fee for a defender -- around £80 million plus add-ons -- to pry Maguire away from the King Power Stadium.
The 26-year-old is set to undergo a medical on Saturday before signing a five-year contract in the next few days. He will be eligible to make his United debut against Chelsea at Old Trafford on Aug. 11.
Leicester were holding out for a bid of £95m for Maguire before agreeing to a compromise. The record fee for a defender eclipses the £75m Liverpool paid Southampton for Virgil van Dijk in 2018.
It brings to an end more than two months of negotiations and secures Ole Gunnar Solskjaer's top defensive target. Maguire had feared Leicester were pricing him out of a dream move to Old Trafford, but after making it clear to the club and manager Brendan Rodgers that he wanted to leave, United have been able to seal a deal.
Manchester City were also interested but pulled out after being told Leicester's demands. Maguire was subject to interest from United last summer but agreed to stay at Leicester and signed a new long-term contract in September.
He played 76 games in two seasons at Leicester after arriving for £17m from Hull City in 2017.
The big-money move for Maguire is the latest in United's planned £200m spend this summer, which ESPN FC reported in May.
Talks between the two clubs in London have progressed well, but sources have told ESPN FC that Dybala has reservations about moving to Manchester and swapping Champions League football for at least one season in the Europa League.
The Argentina forward has returned to Turin to make a decision about his future.