Celta Vigo will approach UEFA if they are unable to resolve the ticket allocation issue with Manchester United for the second leg of their Europa League semi-final tie.
The La Liga club claim they have not received all of their tickets for the May 11 clash at Old Trafford. United, they say, have only made available 1,900 of the 3,780 Celta are owed.
UEFA'S competition regulations state that home clubs are required to set aside at least five percent of their stadium capacity for supporters of the visiting teams.
A Celta spokesman told ESPN FC: "A meeting took place with United in Manchester yesterday [Wednesday] but the ticket issue has not been resolved.
"Celta are demanding United to hand the remaining tickets that the club is entitled to. If the situation is not resolved in the next few days, we will have to ask UEFA to intervene."
The Galician outfit announced that all general tickets for the first leg at Balaidos sold out within 48 hours of being made available to the public.