The centre-back has claimed the club would allow him to move if the opportunity arose and has told them to let him join the Catalans, who are looking to reinforce their defence
The Catalans are keen to sign the French defender ahead of the 2014-15 campaign, with sporting director Andoni Zubizarreta admitting earlier this week that they have tabled an official offer for the 30-year-old.
Nevertheless, Valencia have so far been adamant that they will only let go of Mathieu if Barcelona meet his €20 million buyout clause, much to the dismay of the centre-back, who has set his sights on a move to the Camp Nou side.
"I have no intention to steer toward a confrontation with Valencia, because I respect and love the club and its fans. I am grateful for the faith shown in me in the past five years," Mathieu wrote.
"The goal of this statement is not to force a move away from Valencia, but to shed some light on my situation. Valencia are dealing with an offer from an important club. I am not hiding the fact that this would be a step forward in my career and that it's a unique opportunity any player would take.
"I joined this club on a free transfer five years ago and this transfer would benefit all parties involved. I have always given my utmost for the club, but I think the time has come make the next step in my career. I categorically deny allegations that I am rebelling and refuse to train. I would never run the risk of doing something that could hurt a potential transfer.
"I ask Valencia and its president Amadeo Salva to understand my situation and find a solution. I have the chance to play for one of the biggest clubs in the world and that's all I want now. When I signed a new deal last season, the president promised me that they would be open to a transfer if a good opportunity arose, which is the case now. I want to go for this new challenge and I ask the club to understand my wishes."
Mathieu's current contract with Valencia runs until the summer of 2017.