Elton John has postponed all summer tour dates after an illness that came on during his recent European tour turned out to be much more serious. The singer is undergoing treatment and surgery for appendicitis, but says he'll be back on the road in September.

After a number of blood tests and exploratory scans, John's medical team diagnosed an appendix abscess surrounding retrocaecal appendicitis. A spokesman confirmed the singer won't return to the road until he has fully recovered from treatments and a surgery that's scheduled in the coming weeks.

Doctors will be targeting inflamed toxins within the inflamed appendicitis area. The illness was an obstacle the 66-year-old had to overcome in recent weeks. "To know that he made such super-human efforts and continued to perform to thousands through his illness only confirms his dedication to his European fans," the spokesman added. "He is eager to be back on top form and return to play the remaining shows starting in early September 2013."

John's website reflects the announcement, with a Sept. 4 show in Leeds, England, the next on his schedule. Last month, he released the first single off his new album, 'The Diving Board,' which comes out on Sept. 24.