Whatever you say about U2, you can't accuse the band of not taking risks.

In a moment that may never be repeated in rock history, the veteran Irish rock band invited a covers band on to the stage from the crowd in Toronto's Air Canada Centre to sing a full version of Desire, one of its biggest hits - before an audience of more than 15,000 fans.

Bono with U2 tribute band 'Acrobat' on stage in Toronto. The cover band was invited on stage to play 'Desire' during an official U2 gig. Credit:YouTube

The tribute band, which performs as 'Acrobat', relished the moment, belting out a passionate version of Desire, which topped the charts in Ireland, the United Kingdom and Australia and reached No.3 in the United States. Bono provided backing vocals while lead guitarist The Edge played along.

At the end of the three minute song, the cover band members handed the instruments over to their doppelgangers but not before Bono showed his sense of humour is in tact, telling the the singer, Gabriel Pate: "I've always wanted to meet you."