Bono is disappointed with U2's last album.

The Irish rocker has revealed the band - also made of The Edge, Adam Clayton and Larry Mullen, Jr. - are unhappy with the lack of hit records from their 'No Line on the Horizon' LP and believe its sound is too "challenging" for pop music fans to enjoy.

He said: "We weren't really in that mindset. We felt that the album was a kind of an almost extinct species, and we should approach it in totality and create a mood and a feeling, and a beginning, middle and an end. And I suppose we've made a work that is a bit challenging for people who have grown up on a diet of pop stars."

Bassist Adam also believes their lack of success with singles 'Get On Your Boots', 'Magnificent' and 'I'll Go Crazy If I Don't Go Crazy' are down to huge changes in the industry and how people listen to music.

He explained: "What is rock 'n' roll in this changing world? Because, to some extent, the concept of the music fan - the concept of the person who buys music and listens to music for the pleasure of music itself - is an outdated idea."