Manchester United have been accused of creating tension by tellling fans they risk being attacked ahead of the Champions League clash against Roma.
Rome’s mayor Walter Veltroni is unhappy the club have told travelling supporters to beware of the hardcore “ultras” element of Roma’s support.
Mr Veltroni believes the advice could create a “negative climate”.
He told Italian sports daily Gazzetta dello Sport: “Rome is a city that welcomes everyone in a hospitable manner.
“I consider what appeared on the Manchester United website to be an unfortunate accident, but also dangerous because it risks creating a negative climate.
“I have spoken on the telephone to the English ambassador. Rome is a serene and welcoming city.”
About 5,000 United fans have bought tickets for the first leg of the quarter-final tie and a further 1,000 are expected to travel without tickets.
United boss Sir Alex Ferguson defended the decision to send out the letters, saying it was routine for the club to issue travel advice to its supporters.
“We always issue a letter for every away trip,” he said.
“More importantly, the Italian police have been very communicative with our people.
“Hopefully, everything will be ok. I don’t anticipate trouble but the Italian police are very experienced and I think they can deal with it.”