Liverpool have opened talks with UEFA over the price of tickets offered to Reds fans hoping to travel to Porto next month.
The Portuguese club have charged Liverpool fans €75 (£66.50) to attend the Champions League last-16 second-leg tie in February, the same price as general admission tickets for the match.
However, Porto offer a reduced price of £22 for members' tickets, which are expected to cover the vast majority of the ground in the second leg.
"Liverpool FC has therefore raised this significant discrepancy at the highest level with UEFA and FC Porto, who have confirmed that this pricing structure and policy is in line with previous rounds in the competition," the club said in a statement.
"We will continue our dialogue with UEFA regarding the 50 euro discrepancy between the home and away ticket prices. We will update supporters when those discussions have concluded."
Fellow Premier League clubs Manchester United and Chelsea face Sevilla and Barcelona in their knockout ties. Manchester City will play Basel, while Tottenham Hotspur go to Juventus.