Simon Cowell Simon Cowell

Leave it to Simon Cowell to be Debbie Downer. While Britain's Got Talent contestant and YouTube sensation Susan Boyle has wowed audiences — including Cowell — worldwide, the acerbic judge says he's not ready to declare Boyle his homeland's top Talent.

"There are some acts that you haven't seen yet, it's not quite the one horse race you are going to think this is," Cowell tells British talk show GMTV. "It's difficult to say at this stage because I think we've got to treat it as it is, which is a competition."

Scottish-born Boyle, 47, unemployed and never been kissed, left Talent's initially condescending judges in shock and awe after performing a stirring rendition of Les Miserables' "I Dreamed a Dream." Cowell told her she could "go back to the village with your head held high" and gave her the green light to advance to the next round.

Since then, more than 18 million people have watched Boyle's performance on YouTube and British bookmakers have declared her the odds-on favorite. Boyle also made her U.S. debut on The Early Show Thursday, earning praise from Patti LuPone, who first introduced "I Dreamed a Dream" in 1985. 

Boyle's next talk-show stop? Larry King Live. She will stop by the show, airing at 9 pm/ET, on Friday.