Daniel Levy has no intention of ever selling to the two Manchester clubs again with the Tottenham chairman still regretting allowing Kyle Walker to join City back in 2017.
Levy sanctioned the £45m sale of the England right-back to City and he has been one of the best right-backs in the world in the six years since.
Sportsmail has learned that Levy has never forgiven himself for letting it happen and has vowed never to make the same mistake again.
This policy now represents a major obstacle in United's pursuit of Walker's England team-mate Harry Kane.