Perry, 29, says she was a bit surprised by Cyrus' advances, which is why she spontaneously rebuffed the kiss attempt.
Perry explained that she was just trying to give Cyrus a quick smooch hello, the kind of kiss that most people do as a greeting.
Cyrus apparently thought Perry was coming on to her, so she tried to get a bit frisky. Perry quickly backed away when she realized that Cyrus was trying to makeout with her.
Yeah, I went to her show, which was amazing. It is very colorful. ... She has this one part, where it's like a kiss cam. I just walked up to her to give her like a friendly, girly kiss, as us girls do. Then, she like tried to move her head and go deeper. I pulled away.
Perry said she backed away from Cyrus simply because she didn't know where her mouth had been.
"God knows where that tongue has been," Perry said of Cyrus. "We don't know, that tongue is so infamous."
Perry was likely referring to Cyrus' music video for "Wrecking Ball," where she famously is shown licking a sledgehammer.
Analysis: Cyrus is trying hard to get away from her innocent, Disney child star days. She does everything for shock value these days, and it works in helping her sell tickets and make headlines.
Cyrus is doing what is best for her career, so there was nothing wrong with her playing up the shock appeal with a kiss attempt at Perry.
However, Perry still tries to maintain a classy image, so there was nothing wrong with her backing away from it.