Manchester United are urging Athletic Bilbao to reduce their ticket prices ahead of next month's Europa League tie at San Mames, with the English club set to lobby UEFA if they refuse.
United are likely to receive an allocation of around 2,000 for the last-16 second leg encounter on March 15, but the Red Devils have been shocked to discover that tickets will cost £77.50 - significantly more than athletic charged for their last-32 meeting with Lokomotiv Moscow.
Although it is common practice in Spain for vast disparities in prices to exist for certain games, United feel the sums being charged are excessive.
They have already expressed their concerns to Athletic, but received little sympathy on the grounds that the La Liga outfit intend to charge home supporters exactly the same.
So, whilst they privately accept there is little chance of the situation changing, United feel they must make their feelings known to UEFA too.
It will be the first time the Red Devils have visited the Basque stronghold of Spain since January 1957, when they lost 5-3 in a European Cup quarter-final, only to turn the tie round at Maine Road in the second leg with a 3-0 win.