Carly Rae Jepsen has admitted that she doesn't know what to expect from her upcoming North American tour with Justin Bieber.

However, the 'Call Me Maybe' singer is pretty sure that it will be a definite "whoa" moment.

Jepsen is due to support Bieber as the 'Boyfriend' star promotes his 'Believe' album in the US later this year.

Speaking to MTV, Jepsen admitted that her previous shows with Bieber have rendered her "speechless" and that she believes the next tour will be much the same. She said:

"I don't know what to expect. I did one or two shows with Justin [earlier this year]. One in London and one in Mexico City, and all I can say is, like, 'Wow'. They were huge - 300,000 people in Mexico City. I was speechless. [How do you] take it in? I don't know that I totally do. I think that like in 10 years' time I'm gonna sit back and look at everything that's happening to me this year and actually have a 'whoa' kind of a moment."

She continued: "Right now everything's so fast and the pace of it so quick that I'm just kind of keeping my head to the ground and trying to do the best at getting through it."