U2 have cancelled their headline slot at Glastonbury after singer Bono was told to rest for at least two months following emergency surgery, it was confirmed today.
The singer said he was "heartbroken" after pulling out of the show, which had been booked to mark the festival's 40th anniversary.
Organiser Michael Eavis said it was too early to think about a replacement.
The band have also been forced to postpone 16 shows on the north American leg of their U2360 Tour.
Bono suffered a back injury last week and was discharged from Ludwig Maximilians-University Hospital in Munich, Germany, today.
He has been told by doctors to undertake a rehab regime as well as resting for at least eight weeks.
Bono called Mr Eavis this morning to explain that the band would be unable to play.
He said today: "I'm heartbroken. We really wanted to be there to do something really special - we even wrote a song especially for the festival."
Mr Eavis said: "It was obvious from our telephone conversation that U2 are hugely disappointed. Clearly, they were looking forward to playing the Pyramid Stage as much as we were looking forward to watching them.
"At this point, we have no comment to make about possible replacements for U2's Friday night slot. Instead, we would simply like to send Bono our very best wishes for a full and speedy recovery."
The shelved US shows were due to take place between June 3 and July 19.
Dr Muller Wohlfahrt, who treated the star and recommended emergency surgery, said: "Bono suffered severe compression of the sciatic nerve.
"On review of his MRI scan, I realised there was a serious tear in the ligament and a herniated disc, and that conservative treatment would not suffice."
Bono was said to be in severe pain and suffering partial paralysis in his lower leg.
A ligament surrounding a disc in his back had been torn. And fragments of the disc had travelled to his spinal canal.
Professor Jorg Christian Tonn, who carried out the operation, said: "This surgery was the only course of treatment for full recovery and to avoid further paralysis.
"The prognosis is excellent but to obtain a sustainable result, he must now enter a period of rehabilitation."
Dr Wohlfahrt said: "We are treating Bono as we would treat any of our athletes and, while the surgery has gone very well, the coming weeks are crucial for a return to full health."
He added that rehab would begin in the next few days, with intensity increasing over the next eight weeks.
U2 manager Paul McGuinness, who was at the hospital in Munich, said Bono felt he had let down the audience.
"Our biggest and, I believe, best tour has been interrupted and we're all devastated. For a performer who lives to be on stage, this is more than a blow.
Mr McGuinness continued: "He feels robbed of the chance to do what he does best and feels like he has badly let down the band and their audience - which is, of course, nonsense.
"His concerns about more than a million ticket buyers whose plans have been turned upside down, we all share, but the most important thing right now is that Bono make a full recovery."
He said he was working with promoter Live Nation to reschedule dates.