After the bloody scenes at Roma in the previous round, 4,000 United followers will travel to Italy again on May 2.

But while many observers felt the visitors from Old Trafford were the victims of brutal crowd control tactics by Italian riot police, UEFA are worried about an alcohol-fuelled repeat of the violence.

"There has been a problem with drink and it would be nice if the supporters were advised not to do it," said UEFA spokesman William Gaillard. "I realise this is difficult but people are putting themselves at risk because they stop behaving in a rational way.

"There are no special concerns about the game in Milan. It's a different city, a different stadium and a different team."

There was trouble in Seville last week but none on Tuesday when Chelsea played Valencia.

"If everyone behaves in a proper way, we should have a smooth sailing but Manchester United has to brief its fans and tell them what is appropriate."