Katy Perry has broken up with John Mayer again.

The 'Part of Me' singer - whose divorce from comedian Russell Brand was finalised in July - is said to have told the 'Half of my Heart' singer to lose her number because he cannot commit.

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A source told US gossip website RadarOnline: "John just can't commit, and he kept luring Katy back with promises that was going to change, but then he didn't. Katy was pretty crazy about him, so she kept giving him another chance.

Related: Katy Perry 'totally in love' with John?

"John liked Katy, so he wanted to keep her in his life, but it just wasn't up to Katy's standards. She needs the guy to be on board 100 percent and she was sick of John disappearing for five days at a time, then booty calling her, then straightening up and treating her well, only to go back to his old behaviour a few days later.

"Finally she was like 'lose my number'."

The on-again/off-again couple first began dating in early August but split after just two weeks with friends saying it was only a casual rebound romance following her divorce from Russell. The pair reconciled a few weeks later but this time they have split for good, according to reports.

Katy is preparing to host a divorce party later this month on what would have been her second wedding anniversary on October 23.

Katy and Russell married in a romantic ceremony in India after a year of dating but 14-months later they announced their marriage was over.

A source said: "Katy has been dreading October 23 for weeks now and has been trying to think of ways to turn it into something positive."