In an interview with England's Sun newspaper, frontman Bono said the legendary Irish band is at work on the follow-up to 2009's "No Line on the Horizon."

"U2 have been back and they're really in fine fettle," he said, pushing the rock star's royal "we" to a curious extreme. "They're mad for it at the moment and they really want to make a new record. And they don't care if it takes 10 years -- they don't care if it never happens again, they just want to get it right."

Bono said he and his bandmates -- guitarist Edge, bassist Adam Clayton and drummer Larry Mullen Jr. -- have been calling the album "10 Reasons to Exist," though he added that "at least six" other working titles are in the mix.

In 2011 U2 concluded its ultra-high-tech 360 Tour, which Billboard called the highest-grossing tour of all time. The worldwide trek included a stop at Pasadena's Rose Bowl, where the band played to an audience of nearly 100,000.