George Michael is cancelling a tour of Australia in November and December, saying he needs treatment for major anxiety suffered since his bout of pneumonia last year.
Michael, who made his return to the stage in Vienna in September, said doctors had warned him he would experience "trauma" after the illness and recommended "complete rest and the type of post traumatic counselling which is available in cases like mine."
"I'm afraid I believed (wrongly) that making music and getting out there to perform for the audiences that bring me such joy would be therapy enough in itself," he said in a posting on his website.
"Unfortunately I seriously underestimated how difficult this year would be and although I was right to believe that the shows would bring me great happiness and that my voice would recover completely (I truly think that some of my recent performances have been my best ever) I was wrong to think I could work my way through the major anxiety that has plagued me since I left Austria last December."
Michael spent a month in hospital in Austria last year, coming close to death, after becoming ill during his Symphonic tour.
The former Wham singer plans to keep some dates in Britain in October, but then will undergo treatment.
He apologized to Australian fans for cancelling the nine concert dates, saying that being unable to fulfill the commitment "breaks my heart."