The show must go on! After Justin Bieber kept his fans waiting before taking the stage at London's O2 Arena on Monday, March 4, the 19-year-old singer apologized to concertgoers in a series of Twitter posts March 5.

"Last night I was scheduled after three opening acts to go on stage at 9:35, not 8:30, but because of some technical issues I got on at 10:10. So I was 40 minutes late to the stage," he wrote. "There is no excuse for that and I apologize for anyone we upset. However it was a great show and I'm proud of that."

PHOTOS: Inside Justin Bieber's workout routine

Bieber continued, "Tonight we will run on time and look forward to putting on an amazing show for everyone in attendance. . . . I'm all about the music and performance and I respect my fans. I never have any intent to upset or let anyone down. And I'm not okay with things being exaggerated. Once again sorry for anyone upset. Now we have a show to do today and I'm gonna focus on the positive and put on a grew show tonight here in London. Night 2 at the O2 is gonna be even better. Get ready. Thanks."

PHOTOS: Stars with Justin Bieber's hair

A concertgoer counters that the "As Long as You Love Me" singer didn't hit the stage until 10:38 p.m., after Carly Rae Jepsen and Cody Simpson had finished their sets. To compensate for his tardiness, the concertgoer told Us Weekly that Selena Gomez's ex had to whittle down his set list.

PHOTOS: Celebrities with Bieber fever

Bieber's rep had no comment, but an insider echoed what the singer said via his Twitter account. "He was not supposed to go on until 9:30 and he went on just after 10," the insider told Us. "He was not two hours late. There was no booing."

This article originally appeared on Justin Bieber Apologizes for Delaying London Concert