Not Again! On-Again, Off-Again Celeb Couple Headed For Splitsville For Good?

She has a penchant for bad boys and he's known for going through girlfriends at the speed of knots, so it was probably only a matter of time before Katy Perry and John Mayer called it quits... for the second time.

The high-profile pair have reportedly called time on their short-lived romance but sources are saying that both Katy and John still hope there's room for a reconciliation.

A source close the couple told US Weekly that "it's not over until its over" and that external factors are to blame for the split.

"She's leaving the window open. They have both been so focused on work," another source added.

The former-lovebirds appeared very together at the Grammys earlier this year

The 28-year-old pop princess and the 38-yer-old singer first got together last summer, but split in August 2012, before reconciling a month later, and their relationship seemed to be going from strength to strength with Mayer even visiting Katy's hometown of Santa Barbara, California.

And on March 2nd, all seemed to be going well between the two, with Katy tweeting her 43 million followers that her "boyfriend" was bringing her to a kitten shelter for the afternoon.