Bono thinks U2 are becoming irrelevant.

The 'Invisible' rocker admitted that it has become harder for his band to remain significant in the music industry as they grow older, because the personal experiences they depict in their songs may no longer connect with a mainstream audience.

Speaking during an interview on BBC Radio 1, frontman Bono told Zane Lowe: ''We're on the verge of irrelevance. You have to make stuff relevant to you and where you're at, make an honest account of what you're going through. If that's relevant to other people, great. But we don't know.''

The singer also spoke about the inspiration behind the band's as-yet-untitled 13th studio album, which he claims harks back to when the group - including The Edge, 52, Adam Clayton, 53, and Larry Mullen, Jr., 52, - first got together in 1976.

Bono, 53, explained: ''We went back to why we wanted to be in a band in the first place. We were listening to the Ramones and Kraftwerk - you can hear both on 'Invisible'. It opened up a whole valve for me writing, it was like a damburst of sorts. ''

Bono says the record won't be finished for another two months, but once it's complete the group are looking forward to playing the new tracks in smaller venues.

He explained: ''For this album, we're going to start indoors. We'd like to play the O2 [arena]. Sometimes it's nice to play intimate things like that.''