John Mayer regretfully cancels his upcoming tour as his "granuloma has grown back."

The Gravity singer had surgery on a granuloma, a growth on his tonsils, in October 2011. Although John's recovery from the operation was slow, the musician felt healthy enough to host a 21-date Spring 2012 tour across America beginning this month.

This week, John became clear on the true nature of his throat's condition.

"During rehearsal on Tuesday, it came to mind that I should see my throat doctor because something didn't feel/sound right," John posted on his Tumblr blog Friday. "I went in for a visit on Wednesday and a scope of my vocal cords revealed that the granuloma has grown back where it had mostly healed. This is bad news. Because of this, I have no choice but to take an indefinite break from live performing. Though there will be a day when all of this will be behind me, it will sideline me for a longer period of time than I care to have you count down."

John is not looking forward to the long recuperative process following surgery for this condition.

"I want to explain this a bit more in depth than I have in the past, because I know there's some confusion as to what this condition is; a granuloma forms and continues to snowball because it's in a spot where the vocal cords hit together and there's no way to really give it a chance to heal without a good stretch of time and some pretty intensive treatment," he explained. "In short, it's one giant pain in the a*s."

Although his throat won't be put to use for a while, John is determined to flex his creative muscle and create new music.

"I feel really vibrant as a writer at the moment and there's no reason not to begin the next album project in the time I would have been touring," he wrote. "Somewhere in all of this is another surgery and a very long chemically-imposed period of silence, so I hope you'll understand that I have to really pick that date carefully."

John's new album Born and Raised will be released on schedule on May 22.