AceShowbiz -

On Saturday, September 10, Katy Perry took some time to answer fans' questions on Twitter. When asked if she would work with Taylor Swift, the "Roar" singer revealed she would consider working with her fellow musician, Swift, on one simple condition, which is the "Bad Blood" singer has to apologize to her.

The feud between the two singers started back in 2014, when Swift told the Rolling Stone that her song "Bad Blood" off her album "1989" was about a fellow musician who tried to sabotage her entire arena tour.

"For years, I was never sure if we were friends or not," Swift claimed. "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?' "

Swift added, "She did something so horrible. 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. So now I have to avoid her. It's awkward, and I don't like it."

Fans shortly put the details together and concluded that the anonymous former friend was Perry, who later posted on Twitter, "Watch out for the Regina George in sheep's clothing." While the "Blank Space" singer never confirmed who the song was about, the long-standing feud has yet to be settled.

This Perry-Swift feud resurfaced when DJ Calvin Harris, Swift's ex-boyfriend, addressed the ongoing feud between these two pop stars through his Twitter rant after a messy breakup with Swift last July. "I know you're off tour and you need someone new to try and bury like Katy ETC but I'm not that guy, sorry. I won't allow it," he wrote back then.