After Bono's emergency back surgery, U2 may be forced to cancel their tour until the fall.
The singer was injured when he fell on stage while rehearsing in Munich and was rushed to hospital where he was operated on.
He is said to be making a good recovery but plans for the tour, set to open in Salt Lake City in June, are now on hold.
Manager Paul McGuinness stated that the band will "reinstate the dates" that they will be forced to miss.
It has not been a happy 50th birthday aftermath for Bono, who was hyped up about the resumption of the tour when he spoke at the American Ireland Fund dinner in New York two weeks ago.
Given Bono's need to be highly mobile while on stage, a back injury and surgery could be very tough for him to overcome.
The tour resumption was set to feature several changes in the band's on stage act.
The U2 360 Tour had just paid for itself last year and was set to capitalize on very positive advance bookings when the injury happened to Bono.