04/25/2009 at 02:25 PM EDT
Susan Boyle has become an overnight singing sensation – but that doesn't mean the golden-voiced star will win Britain's Got Talent,
according to show judge Simon Cowell
"I keep saying to everybody, she's got to win the next stage. It's [up to] her," he said Friday in Los Angeles while promoting America's Got Talent.
"She has four weeks to prepare for the biggest time of her life. She's got to sing better than she's ever sung before. But it could all go horribly wrong now because there are so many distractions."
Still, Cowell says that discovering a singular talent like Boyle is exactly the reason behind the show. "This is why we came up with this show in the first place," said Cowell, noting that America's Got Talent
, like it's British counterpart, has no rules about who can audition. Anyone can perform any talent at "whatever age you are – glamorous or un ... We're all guilty on the panel of judging [Boyle] before she sang. We were completely and utterly wrong. It's terribly embarrassing."
Piers Morgan, who is also a judge on Britain's Got Talent
, praised Boyle as well. "Susan Boyle is very good for us," he said. "She's laid down the challenge [as] a talent that comes out of nowhere that can really startle and amaze."
Whether Boyle wins or loses the talent show, she has clearly won many fans. "For someone like Susan, it's once in a lifetime – the world falls in love with somebody," said show judge Sharon Osbourne. "It's unanimous. The world is in love with her."
The Britain's Got Talent
finale is scheduled to air May 24 in the U.K.