Media mogul Simon Cowell has finally joined Twitter and has already entered into a war of words with former Britain's Got Talent colleague Piers Morgan.

Cowell posted his first tweet on the social networking website in the early hours of this morning (November 17) and, at the time of writing, had already amassed over 175,000 followers.

But Morgan, a Twitter veteran with over 1.4 million followers, didn't take long to take a pot-shot at Cowell and his American version of the X Factor. He wrote:

"Save your breath @SimonCowell - nobody's watching X Factor, my show's about to start."

Cowell retorted by telling Morgan to look up 'deluded' in his dictionary, before the TV chat show host upped the ante even further by claiming that he will 'demolish' Cowell. He said:

"Comes before 'demolished' - ironically what I'll do to you on here."

Piers Morgan is currently hosting chat show Piers Morgan Tonight on US channel CNN, while Cowell is busy with his stateside version of the X Factor.

Check out Simon Cowell speaking about the X Factor below: