The club say they are giving the midfielder extra time off to recuperate ahead of the new season. The 33-year-old played 40 times for Burnley last campaign as the Turf Moor club lifted the English Championship crown.
Omitting Barton from the squad also avoids the potential embarrassment of the newest recruit being denied a visa due to his prior conviction for assault and affray back in 2008.
Barton was unable to travel to the United States with the Newcastle squad in 2011 after a temporary visa application for the player was rejected. It is more than likely the American authorities would have taken the same decision this time around.
Mark Warburton’s side will head to Charleston, South Carolina, for a training camp before playing a friendly fixture against USL side Charleston Battery.