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.