Tour behind Perry-Mayer split

John Mayer and Katy Perry. Picture: Getty Images

Katy Perry and John Mayer reportedly split up because of her upcoming world tour.

The Dark Horse singer, 29, was reportedly dumped by the Mayer, 32, because they were arguing a lot and she is "stressed" about her Prismatic concerts, which are scheduled to kick off in Belfast, Northern Ireland in early May and will see her travel across three continents until the end of the year.

A source told UsMagazine.com: "She's stressed about the tour, they've been fighting. It is probably for the best, because she is going to be on tour for forever. Of course this happens all the time, I can't keep track anymore. But for now they are done."

The duo, who released the romantic duet Who You Love in December, first began dating in summer 2012 and had an on/off relationship until things became serious between them last year, after Perry publicly admitted she was "still madly in love with him."

A friend predicted they could reunite again, saying: "Not sure how long it will last this time but yes, it is off for now."

But a third source said: "They've had rough patches, but this may be for good."