Bono has revealed the Irish rockers have recorded "several" albums in the last five years but scrapped them because they were not good enough to release.
The singer said the band had spent two years working on their latest album, Songs Of Innocence, which was given away to 500 million iTunes customers last month in a deal with technology giant Apple.
He told Q Magazine: "Rumour has it we haven't made a U2 album in the last five years. We have. We just didn't release them because we were waiting for something that would be as good as the best we've ever done. That was the standard. Or else, why bother?"
The new album was released to mark the launch of the iPhone 6, but did not go down well with everyone and Apple had to create a tool that allowed customers to delete the tracks.
Bono said he was still "against free music" despite the deal, telling Q: "We're not giving it away. Apple are giving it away. This is really important."