A new report claims that pop princess Katy Perry has turned down a marriage proposal from her beau John Mayer.

According to Grazia magazine, singer-songwriter John was keen to prove his commitment to Katy by popping the question, but a source claims the Roar songstress "doesn't feel ready" to wed again.

The source told the publication: "John won't run from Katy again. He knows his bad-boy reputation and what happened with Russell hurt Katy, and he'll do whatever it takes to show he's the one she should marry."

"John's proposal really unnerved Katy. Even though they have discussed it, she thought it was too soon. John was gutted."