The rock star heaped criticism on Cowell's British version of American Idol – The X Factor – describing the show as "appalling" and promoting bland, soulless music in an interview with the London Evening Standard.
"It's a preposterous show, and you have judges who have no recognizable talent apart from self-promotion," Sting, 58, said. "Basically I was looking at televised karaoke where they conform to stereotypes. It is a soap opera which has nothing to do with music."
One of those judges, of course, is Cowell, 50, who offered a riposte to Sting's stings on Saturday's live X Factor show.
"Talking about these contestants being a bunch of karaoke no-hopers … I thought it was pompous," he said, before inviting Sting to come on the show as a mentor.
On Sunday, Cowell followed up again on The Xtra Factor. "Someone has got a little bit grumpy," he joked with his co-judges. "We'd like a Sting week."
But he later admitted: "He hasn't called yet. We're waiting!
Don't hold your breath, Simon. In his interview, Sting made it clear he had no interest in setting foot on the X Factor stage.
"I wouldn't get on The X Factor because I don't sound like anyone they're after," he said. "I sound like myself. I think they are basically aping pre-existing stereotypes of what singers should do and they're not being themselves."