Simon Cowell Sings On The X Factor USA

The X Factor USAby bursting into song.

The famously stern reality TV mogul appears to be softening in his old age, having been on stage during an episode of Britain's Got Talent earlier this year.

SiCo was reportedly persuaded into warbling by his fellow judges Demi Lovato, Paulina Rubio and Kelly Rowland after a disappointing day of auditions in Denver, Colorado.

According to The Sun, Demi told one hopeful who had performed in a dodgy British accent: "You would sound like what Simon sounds like when he sings."

And Kelly then urged Cowell to have a crack at the same tune, Fools Rush In - with the three other judges passing comment on his effort afterwards.

Demi said his singing was "charming", while Paulina claimed it was "great" and Kelly added: "I knew that voice was always there."

Meanwhile the first episode to be aired in the US has received a positive reaction from critics.

The Hollywood Reporter wrote of the judges: "The foursome seem genuinely comfortable together and have a chemistry that blows Britney Spears out of the water."

CHECK OUT PICS OF FROM THE X FACTOR USA 2013 HERE!