U2 frontman Bono has admitted that he has been disappointed by the lack of success of their 2009 album 'No Line On The Horizon'.

The band's twelfth studio LP shot straight to the top of the UK album chart when it was released in March and has sold a respectable 1 million.

But the LP, is the group's lowest selling in more than a decade, with 2004's 'How to Dismantle An Atomic Bomb' selling 3.2 million copies to date and 2000's ''All That You Can't Leave Behind' clocking up sales of 4.3 million.

The album's first single from the album 'Get On Your Boots' peaked at number 12 in the single charts and 'I'll Go Crazy If I Don't Go Crazy Tonight' only reached number 32.

Bono admitted that he was disappointed that the band didn't "pull off the pop songs".

He told spinnermusic: "We weren't really in that mindset and 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."