The group was slated to play in Philadelphia on July 12th.
"Our biggest and I believe best tour has been interrupted and we're all devastated," manager Paul McGuinness was quoted as saying.
U2 was to begin its North American leg of the tour on June 3 in Salt Lake City, Utah, perform in cities such as Toronto, Seattle and Denver, and give a final concert in New Jersey on July 19 before heading to Europe.
It was unclear if the latter portion of the "U2360°" tour will take place as planned, but the concert dates are still confirmed on the Web site.
Bono had injured his back while preparing for the North American leg of the tour and underwent emergency surgery in Munich, Germany on Friday. The first U.S. tour date was canceled last week. Bono has since been released from hospital.
U2 has also canceled its headlining performance at the popular Glastonbury Festival in the United Kingdom next month.
