It was supposed to be the most memorable performance in Glastonbury's history, but Bono has been left "heartbroken" after U2 were forced to cancel their headline slot at this year's festival following the singer's back injury last week. Organisers confirmed that U2 would have to pull out earlier today, saying: "We are just gutted, it is really terribly sad."

The singer is following medical advice to cancel forthcoming performances after undergoing emergency surgery for severe compression of the sciatic nerve. The injury occurred during rehearsals for their world tour last Friday. The band then cancelled a string of live shows while the 50-year-old singer recovered in hospital.

Bono released a statement through Glastonbury festival, saying: "I'm heartbroken. We really wanted to be there to do something really special – we even wrote a song especially for the festival."

Glastonbury organiser Michael 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."

A spokesperson for the festival responded to speculation about who would replace U2: "We won't be making any comment about who will headline on Friday. Bono has only just got out of hospital, he is not in a good way. It would really be a bit crass if we start talking about who was to replace them."

Following the announcement of U2's headline performance in November 2009, Eavis said: "We've been trying for years ... And now we've finally made it happen. I'm sure they will pull out all the stops to make next year's Glastonbury the most memorable ever."

U2 were in the middle of a world tour that has been described as the "biggest rock tour in history", thanks to the sheer scope of its ambitious set design.

The tour had been projected to gross $750m (£524m) by the end of 2010.

Forthcoming dates for U2's North American tour have been also been postponed. The band have promised to reschedule all dates for 2011.

The Guardian is the official media sponsor of Glastonbury festival, which takes place on 25-27 June.