Coldplay and Dizzee Rascal are the top choices to replace U2 at Glastonbury as fears grow about the state of Bono's health.
The Irish super group were set to headline the massive Brit pop festival event on June 25 but they may be forced to pull out over Bono's back injury.
Bono injured his back in Germany last Friday while rehearsing for the 360 Tour, forcing the cancellation of several of the band's U.S. tour dates.
He was operated on by the same neurosurgeons who look after Germany's famed soccer team, Bayern Munich.
He is expected to return to Ireland over the next few days to recuperate.
Band manager Paul McGuinness refused to clarify the injury, saying only that a statement is expected in the next few days.
However, he admitted that the surgery had been "very disruptive" for the U2 tour crew.
"We have over 400 people converging on Salt Lake City and some of those have been turned around and told to stay at home until we make our new plan,” he said.
U2 were just about to start the second leg of their 360 Tour with a concert in Utah on June 3.
Fans are being advised to monitor the U2.com website.