Fergie is worried about supporting U2 as she is such a fan.

Black Eyed Peas are set to open for the 'One' rockers at five shows on their forthcoming world tour and the singer admits she will find it "challenging" as they were one of her favourite groups as a teenager.

She said: "It's going to be amazing. I remember going to see U2 in high school - I went on two different dates to U2 concerts, so now to be on that stage, it's going to be challenging. We definitely have to bring it at those shows."

The 'Boom Boom Pow' hitmakers are currently preparing for their biggest-ever headlining shows and Fergie admits it is a radically different experience to their previous performance planning.

She explained to Billboard.com: "It's going to be the biggest tour, production-wise, that we've ever done. We're actually planning for that now, which we've never done before -- actually plan for a tour.

"It's usually just learn the songs by performing at festivals and that's our show. But now we're stepping it up. We had some visuals before, but now we are going to have a lot more, and we're really excited about that."