Irish American bad boy Charlie Sheen.Getty Images

The 'Anger Management' star, who branded the 'Keeping Up with the Kardashians' beauty "a pox on the face of entertainment" after accusing her of refusing to sign an autograph for a six-year-old fan, is now "really embarrassed" by his actions and posted a message asking for forgiveness on Twitter.

He wrote: "Dear Kim, my extreme bad. really embarrassed by my actions. I was already p***ed about some other c**p that had nothing to do with you. I heard a story that bothered me. wrote some trash you didn't deserve. Ever. I'm an idiot as often as I'm a genius. that day, clearly I was the former. xox"

The 49-year-old star's apology came just hours after he insisted he was standing by his earlier social media attack on the reality TV star, 34, and said she had "zero gratitude, zero awareness, zero talent, a pox on the face of entertainment she is!"

The outspoken actor lashed out at Kim after his friend claimed that she was very unpleasant to a young fan who approached her for an autograph in an empty parking lot and told her assistant: "Oh God, can you handle this."

Charlie alleged: "The assistant and dooshy got in her car and pulled out and sped past the poor little six-year-old without even a glance to the child."

A source close to Kim, who has 18-month-old daughter North with husband Kanye West, previously insisted the incident never took place and claimed she said: "I never say no to autographs, especially kids."