Singer Usher reportedly regrets his friendship with singer Justin Bieber and also finds him arrogant.

The "Pop Ya Collar" hitmaker was Bieber's showbiz mentor at the start of his career and regrets his decision, reports showbizspy.com.

Usher has allegedly slammed the 20-year-old calling him "arrogant", "ungrateful" and "dumb" and told his friends: "Do not ever refer to that punk as my protege!"

`Usher was so incredibly supportive of Justin that he even flew to Panama in January after his Miami arrest, hoping to talk some sense into him, which did no good,` said a source.

`But the straw that broke the camel's back came when Usher saw TV news footage of Justin's sneering, arrogant deposition in court."

"He was not only disrespectful and rude to the attorneys, but when Usher's name came up, the ungrateful brat barely acknowledged he even knew the star and gave him no credit for his success," added the source.