Niall Horan, Mullingar star of One DirectionGoogle Images

As One Direction play the opening nights of their first headline tour in the U.S. this week, Niall Horan has been speaking about the group’s rise to stardom.

In conversation with Digital Spy, Horan spoke about dealing with nerves when the band play arenas in the U.S.

"When we first started out the thought of getting up on stage freaked us all out. The kind of crowds we get are very, very loud, which helps," he said.

“The venues are a bit bigger out here - I think tonight's venue holds about 9,000 people. The smallest show is 6,000 and the biggest is 20,000."

"The bigger the crowd the better really! The noise calms your nerves."

Speaking about One Direction’s screaming female fans, Horan said it’s hard to get used to.

“You can see girls getting too excited and they start crying or worse. In a lot of these countries they don't get a lot of gigs to go to, so when they get to see their favorite artist they take full advantage of it. Obviously the excitement builds up too much for some on the night and they get a bit...crazy."

“Sometimes I've seen some stuff that's a bit too much!” he added.

The teenager also said the boys hope to release their second album by the end of the year.

"We've got some great songs that we're very excited to bring out and can't wait for the fans to hear. We're hoping to get it out towards the end of the year."

Horan also admitted he was starstruck when he met Michelle Obama, “She's an amazing-looking lady, and I'm a massive Barack Obama fan anyway.”

The only Irish member of One Direction, Horan said he will never forget the first time he met Katy Perry.

“Katy Perry still gets me every time. She's very funny in person! We met at the Teen Choice Awards and she pulled my cheeks apart and told me how cute I was. My life was literally flashing before my eyes!"