A total of 1,400 Italian officers will be on duty for the football match
Manchester United fans in Rome for the Champions League quarter final are being warned not to rely on the British consulate if they get into trouble.
The warning follows a number of matches between United and AS Roma which have been marred by violence.
A total of 1400 Italian police will be on duty in and around the stadium - a ratio of one officer to every three Manchester United fans at the game.
The football match is set to kick off at 1945 BST.
Matthew Donnelly, from the British Consulate in Rome, said: "If someone is taken to prison we can visit them if they request it and we can put them in touch with local lawyers if they need one.
"I should stress that we can't get them out of jail, we don't have a magic wand and can't give them a 'get out of jail free' card nor can we represent them in court."
Officers from Manchester recently flew to the Italian capital to discuss policing and have been monitoring British airports to target known troublemakers attempting to travel to Italy.
It is the fifth time the two clubs have met in the Champions League in less than a year.
In the 2007 quarter-final, three United fans were stabbed outside the Stadio Olimpico.
Scuffles also broke outside Old Trafford during the second leg, with 21 people arrested.
The teams also played each other in the group stage of this season's competition and four Manchester United fans were jailed in Italy for clashing with rival fans in Rome in December.
Fans without tickets for the game have been warned not to travel to Rome and Italian authorities have taken several precautions to avoid a repeat of previous clashes.
Free transport has been organised for United fans in a bid to avoid trouble previously seen on the Duca d'Aosta bridge.
In addition, United fans will only be able to pick up their ticket at a designated ticket collection point 24 hours before the match and will need their passports as proof of identity.