From next season, teams in the top flight will not be able to bring in new players after 5pm on the Thursday before the new campaign commencing.
The Daily Express claim 14 clubs voted through the motion but the Manchester giants were not in favour of the bold change.
Arsenal, Tottenham, Liverpool and Chelsea are all said to have backed the idea with one Premier League club choosing to abstain.
A statement from the Premier League explained the changes.
It read: “Premier League Clubs have today agreed to a rule amendment that will see the summer transfer window in any year at 17.00 on the Thursday before the start of the Season.
“This is for Premier League clubs only and has no bearing on other leagues and competitions.
“The first transfer window in which this applies will be the summer transfer window in 2018 (ahead of the 2018/19 season) and it will close on 17.00 on Thursday 9 August 2018.”
United and City were among the biggest spenders in the Premier League this summer.
The Red Devils added Victor Lindelof, Romelu Lukaku and Nemanja Matic to their ranks.
City brought in Benjamin Mendy, Kyle Walker, Bernardo Silva, Ederson and Danilo as Pep Guardiola looks to challenge for the Premier League title.
