Simon Cowell is to sing on 'X Factor' USA.

The music mogul is persuaded to show off his vocal talents by fellow talent show judge Kelly Rowland during auditions in Denver, Colorado, after being less than impressed with one wannabe's attempt at singing 1940s classic 'Fools Rush In'.

Following the hopeful's rendition, judge Demi Lovato told them: ''You would sound like what Simon sounds like when he sings.''

Kelly then urged the 53-year-old star, who branded the auditions the ''worst'' day of try-outs ever, to sing the same song.

Simon, who has always vowed to never sing in public, obliged and was praised by fellow judges Paulina Rubio and Demi, who said his rendition was ''charming''.

Kelly added: ''I knew that voice was always there.''

The episode featuring Simon's singing will be screened in the US tonight (12.09.13) and aired in the UK on ITV2 on September 20.

Meanwhile, Simon, who is expecting his first child with US socialite Lauren Silverman, joked he might have a few children around the world.

He quipped: ''I have probably got a few kids dotted around -- there are a few rumours.''