Rita Ora will be a ''superstar'', according to Iggy Azalea.

The Australian rapper has boldly predicted worldwide success for her close pal, who she recently collaborated with on new track 'Black Widow', which was penned by Katy Perry.

Iggy said: ''Rita's a superstar and she will only get bigger. She's one of those girls that always gets the party started, she is so mischievous, it's great going out with her.''

The 23-year-old star was originally determined to avoid any collaborations on her debut album, 'The New Classic', but eventually relented when 'Roar' hitmaker Katy pitched 'Black Widow' to her.

She explained: ''I changed my mind when Katy said she kept thinking of me when she wrote 'Black Widow', but it was months before I got to hear the song. I was going, 'Play me the damned song! What the hell?' ''

Iggy also reveals that Katy was her first choice to sing on the track but the in-demand star couldn't fit a recording session into her busy schedule.

The rapper told the Daily Star newspaper: ''Katy couldn't get time to sing on the track herself, so we wondered who else could do it. It needed someone who could really sing, as Katy's voice is awesome. Rita is a great fit - her voice can blow people away.''