U2 has been forced to withdraw from its headline slot at Glastonbury festival in the U.K., following medical advice for frontman Bono. He will be out of action for at least eight weeks.

The band had been booked to play its first ever Glastonbury festival on June 25, headlining the Pyramid stage. A replacement act has yet to be confirmed for the opening Friday night of the 177,000-capacity event.

Bono called Glastonbury organizer Michael Eavis this morning (May 25) to break the news that, as a result of the serious back injury sustained by the singer last week, the band would not be able to play the festival in a month's time. Bono had emergency surgery after the injury.

"I'm heartbroken," said Bono in a statement. "We really wanted to be there to do something really special - we even wrote a song especially for the festival."

Eavis added: "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."

There are reports that rapper Dizzee Rascal will move up the bill to headline, or even that Eavis will get Coldplay to perform.

Live Nation, promoter of the U2360° tour, today confirmed that 16 shows from Salt Lake City (June 3) to New Jersey's Meadowlands Stadium (July 19), will be rescheduled for 2011.

The tour is the most expensive ever staged, and any postponement means its huge running costs, including the wage bill, still have to be covered.

"Although we understand the disappointment to U2 fans, first and foremost comes the recovery of Bono," said U2 tour producer/promoter Arthur Fogel, CEO of Live Nation Global Touring, in a statement.

Details on rescheduled dates will be confirmed shortly, according to a statement.

The injury was sustained during tour preparation training.

According to the U2 Web site, Bono has now been discharged from Ludwig Maximilians-University (LMU) Hospital in Munich where he underwent emergency surgery. He is under doctor's orders to start a rehabilitation program and to recuperate for at least eight weeks.

"Bono suffered severe compression of the sciatic nerve," the site quotes Dr Muller Wohlfahrt. "On review of his MRI scan, I realized there was a serious tear in the ligament and a herniated disc, and that conservative treatment would not suffice. I recommended Bono have emergency spine surgery with Professor Tonn at Munich's LMU University Hospital on Friday [May 21]."

Professor Tonn, who carried out the operation, added: "He was already in severe pain with partial paralysis in the lower leg. The ligament surrounding the disc had an 8mm tear and during surgery we discovered fragments of the disc had traveled into the spinal canal. This surgery was the only course of treatment for full recovery and to avoid further paralysis. Bono is now much better, with complete recovery of his motor deficit. The prognosis is excellent but to obtain a sustainable result, he must now enter a period of rehabilitation."

Wohlfahrt said that "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. In the next days, he will start a light rehabilitation program, with increasing intensity over the next eight weeks. In our experience, this is the minimum time."