Simon Cowellhas admitted he is nervous about launching The X Factor USAas heworriesits failure could end his US career.

"This better bloody work or I am in huge trouble,” he said of the show, which launches in September. Part of the pressure is due to the fact that it is the most expensive reality show in history, costing just shy of $3.4m per episode.

In a new interview with the Wall Street Journal, the X Factor boss also admitted he had grown bored with the UK series, but that his disillusionment led to the idea to launch the show in America.

Simon said the tipping point was auditions in Glasgow a couple of years ago. “I literally stood up and said, 'I can't do this anymore'. So we got back on a plane. I was in a filthy mood,” he recalled. “I thought, ‘This show is boring. I don't want to do it anymore’.

“Then I got an idea,”he continued. “I wanted to shoot the auditions in an arena, like concerts."

So live auditions were set up, the first of which took place in London in front of 5,000 fans. "That's when it crossed my mind that this show is absolutely coming to America,"he revealed.

As previously reported on MTV, Simon recently dropped in to the UK auditions to [uuid=d33a486a-cd45-4197-bf68-6d00ed038784]Kelly Rowland, to up their game.