Keith Richards reportedly called Justin Bieber ''a wannabe.''

The Rolling Stones rocker was initially unimpressed with the 20-year-old singer during a chance encounter at a ''tiny beach bar'' on the luxurious Parrot Cay island in the Turks And Caicos last month, but they ended up bonding over a few drinks together.

An eyewitness said the 'Boyfriend' singer arrived at the resort where ''there was an old guy throwing back drinks who said, 'Who the f**k are you?' [and Justin replied] 'I don't know, who the f**k are you?' ''

The 71-year-old British star was amused by Justin's attitude and responded: '''You're a man. I respect that,'' before he walked away.

The Canadian heartthrob only realised who he had been talking to when ''another old guy came over and told Justin, 'Keith Richards wants to have a drink with you.' ''

The source claims Keith told the young star, ''Let's get one thing straight. You're a wannabe'' when Justin ''tried to bro down with him.''

But the insider told Us Weekly magazine that the duo ''swapped numbers'' after they had a long talk, adding: ''Justin called it the best night ever.''