Greater Manchester Police (GMP) have warned fans they will crack down on any troublemakers at Sunday's FA Cup derby clash at the Etihad Stadium.
There have been problems at City home games against United in recent seasons, with 29 arrested after the Carling Cup semi-final first-leg tie two years ago. Further disturbances have scarred the latest contests and there are fears the size of United's 5,700 visiting contingent this weekend creates the potential for even more problems.
GMP Assistant Chief Constable Terry Sweeney said: "The close rivalry between the clubs really adds something extra to this fixture and should be embraced. But we must also ensure that this is not used as an excuse by some individuals to carry out football-related violence and disorder."
He added: "Both clubs have been working closely with police in the lead up to the game to ensure the event is a safe and enjoyable one for all who attend.
"In recent derbies the vast majority of fans have enjoyed themselves and behaved impeccably and the number of arrests we have had to make has been relatively low considering the number of people who attend.
"And we do make it clear to the minority of fans who may be thinking of causing any trouble that we will clamp down hard on them."
Fans who are caught misbehaving run the risk of lengthy bans from stadiums.
Police patrols will be in place, both in the city centre and around the ground, while officers will be visiting pubs where the match is being shown live on TV.