Katy Perry won't be falling for sob stories on 'American Idol'.

The 'Chained to the Rhythm' hitmaker is set to take her place on the judging panel of the US talent show soon but she insists she won't be following her heart but her head when choosing who she thinks should go through.

She said: ''Sob stories come second for me. I just want to give constructive criticism - if you don't got the goods, you don't got the goods. The marketplace is already way too crowded, there's 100,000 things coming out every Friday - we don't need another person just to fill the space. We want a star and we need a star.''

And Katy ''really respects'' former judge Simon Cowell for always being honest and truthful.

She added: ''I really respect [Simon] because he was just truthful. He's seen it. I don't need to be there to win the popular race. I want to make someone's dreams come true.''

There is still a space to fill on the 2017 judging panel and Katy is rooting for Lionel Richie and Charlie Puth.

Speaking on On Air with Ryan Seacrest, she shared: ''I'm really pulling for Lionel, because I think Lionel Richie is an icon ... If you've ever seen or met Lionel, he just knows how to charm the whole room. His presence brightens the whole room.

''Charlie Puth is somewhat new to the general public of America. He has his own big fanbase, but I think he's really talented and Attention is one of my favorite things. He's young, fresh, cool, hip.''