Katy Perry's romance with John Mayer is back on.

The on-again/off-again couple were spotted celebrating John's 35th birthday in New York together yesterday (16.10.12) less than a week after the 'Part Of Me' singer dumped the 'Half My Heart' singer telling him to lose her number.

They enjoyed a romantic lunch together at New York's trendy ABC Kitchen to celebrate John's special day and sources say Katy was hoping to get more serious with him before their most recent split.

A source told the New York Daily News: ''She's been really depressed and needs attention. She really liked him and thought it was going to be something serious.''

The couple - who first started dating in June - were also seen having dinner at Pearl restaurant in the city before going clubbing together on Sunday night (14.10.12).

Their latest reconciliation comes just days after sources claimed Katy had grown tired of John's failure to commit.

A source said: ''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'.''

Katy - who will celebrate her 28th birthday on October 25 - is preparing to host a divorce party later this month on what would have been her second wedding anniversary with Russell Brand on October 23.

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.''