The Cause Of Taylor Swift And Katy Perry Beef Revealed.

Taylor Swift has some bad blood with Katy Perry - and the pop singer isn't taking it lying down.

The feud came to light after Swift told Rolling Stone for a cover profile released yesterday that the angriest song on her new album is about another female artist she declined to name.

''For years, I was never sure if we were friends or not,'' the crossover country-pop songstress told the magazine. ''She would come up to me at awards shows and say something and walk away, and I would think, 'Are we friends, or did she just give me the harshest insult of my life?'''

But then last year the other star took things up a notch.

''She did something so horrible," Swift said. "I was like, 'Oh, we're just straight-up enemies.' And it wasn't even about a guy! It had to do with business. She basically tried to sabotage an entire arena tour. She tried to hire a bunch of people out from under me.

''And I'm surprisingly non-confrontational - you would not believe how much I hate conflict. So now I have to avoid her. It's awkward, and I don't like it."

But that didn't stop Swift, who has famously written songs about her failed romances, from penning a song called Bad Blood about the failed friendship. The album, titled 1989, won't be released until next month.

Internet sleuths quickly began deducing whom Swift was talking about. All signs pointed to Perry - who earlier this year split from Swift's ex-boyfriend John Mayer, the infamous subject of Swift's takedown song Dear John. Perry also hired three of Swift's back-up dancers last year in the middle of Swift's Red tour to go work on Perry's Prism tour. (All three had previously worked with Perry).

One of the dancers, Australian Lockhart Brownlie, said last year that Perry recruited them personally.

Dancing with Taylor ''was a great experience and she's a great person to work with, but then Katy contacted us,'' Brownlie told the Tasmanian Examiner. ''Obviously we were with Katy for 2 1/2 years, she's like family to us, so we were, like, 'absolutely'''.

Perry appears to have confirmed the feud, tweeting today.