Katy Perry: I'll work with Taylor Swift if she apologizes

LOS ANGELES, Sept. 12 (UPI) -- Katy Perry is open to working with Taylor Swift... on one condition.

The 31-year-old singer told fans in a tweet Saturday that she's willing to collaborate with Swift if the 26-year-old star apologizes for their reported feud.

"If she says sorry, sure!" Perry wrote in response to a fan asking, "Will you collab with Taylor Swift?"

Perry's conflict with Swift began in 2014 when Swift hinted to Rolling Stone that her song "Bad Blood" is about a fellow singer. Swift claimed the unnamed person nearly destroyed a headlining tour.

"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," the star said.

Social media users speculated Swift was talking about Perry, who tweeted, "Watch out for the Regina George in sheep's clothing," a day after the interview was published. Perry later told Billboard, "If someone is trying to defame my character, you're going to hear about it."

Most recently, Swift's ex-boyfriend, Calvin Harris, appeared to confirm the feud by saying Swift was trying to "bury" him "like Katy" by revealing she wrote his song "This is What You Came For." Perry subsequently tweeted a gif of Hillary Clinton making a face and shrugging.