"We have made a decision to increase the ticket prices for Sevilla fans for the game at Old Trafford, and use this increase to subsidise our fans".
Manchester United took the decision after Sevilla refused to lower the price despite numerous requests.
Sevilla fans on a European night.
The whole thing started when La Liga side Sevilla chose to charge the visiting fans section €100 per ticket which prompted outrage from Man United fans and the club itself in getting involved in trying to convince Sevilla to lower the price.
It's ridiculous that the situation has got to this point - particularly with fans on both sides now set to lose out.
United say they would have to move part of the away support to the top of the East Stand, which police have advised against, if they allowed 3,800 Seville fans into the stadium.
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"This has been raised with Sevilla, and internally, but ultimately Sevilla have not agreed to significantly lower the price of tickets for our fans to what we view as a reasonable level".
It had escalated when Manchester United informed their travelling supporters their first leg tickets to the Spanish match would be subsidised by charging Sevilla fans more for the second leg.
A club statement read, "In this instance we believe that our travelling supporters are unfairly being subjected to increased/excessive ticket prices from the host club".
They have also said any extra revenue raised after refunding fans will be donated to the Manchester United Foundation.
The Manchester United Supporters Trust (M.U.S.T) praised the club.
United were given 2,450 tickets priced at £89 (€100) for the clash with Sevilla, with a further 200 tickets priced at £133 (€150).
"Our primary objective was to ensure our fans didn't end up paying this much".
And in an escalation of the conflict, they have now threatened to report United to Uefa claiming they break the competition's ticketing regulations.