Uefa has issued a warning to Manchester United and Chelsea fans without a ticket for the Champions League final on 21 May - do not travel to Moscow.
European football's governing body has struck a deal with Russia where visa requirements for the 42,000-plus fans with tickets are waived for 72 hours.
But Uefa spokesman William Gaillard has told BBC Sport that its advice for fans without tickets is: "Don't go there.
"Spare yourself the aggravation of being rejected at the stadium."
Uefa announced the three-day visa exemption on Monday, with president Michel Platini thanking the Russian government for an "exceptional and unprecedented gesture".
"I would tell the fans 'be reasonable, stay put'. It's going to be expensive"
Applicable between 19 and 23 May, it means supporters will need to present a valid match ticket, valid passport and a completed immigration form upon arrival to gain entry into Russia. That move means that the situation for fans with tickets - which have already been issued by the clubs - becomes crystal clear.
But it also further complicates matters for Chelsea and United fans pondering whether to travel to the Russian capital.
Uefa, however, insists that conditions would not be favourable for ticketless supporters.
Gaillard added: "I would tell the fans 'be reasonable, stay put' because otherwise you are going to have to pay for a full visa, it will be complicated to get it in most cases as you will have no proof of hotel reservations - and, of course, no ticket. It's going to be expensive.
"The Russian authorities are going to be very strict about people trying to get into the stadium with counterfeit tickets or tickets that don't really belong to them.
"People who are not sober will also find it difficult around the stadium because the Russian law on alcohol consumption is very tough."
Gaillard said that although there will be a designated 'Fans' Park' in Moscow in which to watch the game, he questioned the wisdom of travelling across Europe just for that experience.
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"Is it worth spending all that money just to go to a Fans' Park when I'm sure there will be plenty of public places in the UK showing the game," he said.
United and Chelsea have been given 21,000 tickets each for the final at the Luzhniki Stadium, where the capacity is being set specifically at 69,500.
Any supporters with tickets overstaying the 72-hour entry period will have to pay the fee for a regular visa when leaving the country.
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