Arsenal captain Laurent Koscielny refused to travel on the club's pre-season tour of the United States after a request to have his contract cancelled was rejected, PA understands.
The 33-year-old was due to fly out to the USA with the rest of the squad on Thursday but the club announced earlier in the day that the defender would not be travelling.
It is understood Koscielny, whose contract runs until next year, made it clear to the club that he wish to be released from the agreement this summer in order to sign for another club.
But Arsenal have stood firm and, upon their refusal to grant the former France international a free transfer, Koscielny responded by not joining his team-mates in the USA.
"Laurent Koscielny has refused to travel to the US for our pre-season tour," a club statement read.
"We are very disappointed by Laurent's actions, which are against our clear instructions.
"We hope to resolve this matter and will not be providing any further comment at this time."
Internal disciplinary proceedings will begin against Koscielny in the coming days as the rest of Unai Emery's squad prepare for the new Premier League campaign.
Koscielny's future is now in doubt ahead of the season opener at Newcastle on August 11 and the situation may leave Arsenal needing to recruit another centre-back in the transfer window.
They are closing in on the capture of Saint-Etienne's 18-year-old defender William Saliba but that deal is expected to see the teenager return to the Ligue 1 side on loan for the next season.
Koscielny did not feature for the Gunners until December last season, spending seven months on the sidelines overcoming a serious Achilles injury suffered in Europa League semi-final defeat to Atletico Madrid last May.
He has made 353 appearances for Arsenal since joining from Lorient in 2010, scoring 27 goals and winning two FA Cups.
