"Let's see how much money Fox is going to make on the debate without me," Trump said in a press conference in Marshalltown, Iowa, Tuesday night. "It's time that somebody plays grownup."
"He will not be participating in the Fox News debate on Thursday," Trump's campaign manager, Corey Lewandowksi, told The New York Times, adding "it's not under negotiation."
The move comes just after Fox News announced the debate lineup.
The debate, set for Thursday evening in Iowa, will air on Fox News -- the last chance for GOP presidential hopefuls to appeal to voters before the Iowa caucuses on Feb. 1.
Trump told CNN's Wolf Blitzer on Monday: "I don't like her, she doesn't treat me fairly. I'm not a big fan of hers at all, I mean, I don't care. I might be the best thing that ever happened to her, who ever even heard of her before the last debate?"
Blitzer asked whether or not that meant Trump would appear at the debate.
"If I think I'm going to be treated unfairly, I'll do something else," Trump responded.
After the remarks, Fox News told Mediaite: "Sooner or later Donald Trump, even if he's president, is going to have to learn that he doesn't get to pick the journalists—we're very surprised he's willing to show that much fear about being questioned by Megyn Kelly."
Kelly told her viewers as well: "I'll be there. ... The debate will go on with or without Mr. Trump."
A spokesperson for Fox took a more sarcastic tone when speaking with Business Insider Tuesday afternoon:
"We learned from a secret back channel that the Ayatollah and Putin both intend to treat Donald Trump unfairly when they meet with him if he becomes president — a nefarious source tells us that Trump has his own secret plan to replace the Cabinet with his Twitter followers to see if he should even go to those meetings."
The history of Trump versus Kelly
The feud between Trump and Kelly began with the first Republican presidential debate in August. Kelly asked Trump about misogynistic comments he made in the past.
"You call women you don't like 'fat pigs,' 'dogs,' 'slobs'' and 'disgusting animals,'" Kelly said, before Trump interrupted her to say: "Only Rosie O'Donnell," to laughter.
Kelly went on: "Your Twitter account has several disparaging comments about women's looks. You once told a contestant on Celebrity Apprentice it would be a pretty picture to see her on her knees. Does that sound to you like the temperament of a man we should elect as president, and how will you answer the charge from Hillary Clinton, who was likely to be the Democratic nominee, that you are part of the war on women?"
Trump responded by saying the problem was not with his remarks, but with people being too "politically correct." He added: "And honestly Megyn, if you don't like it, I'm sorry. I've been very nice to you, although I could probably maybe not be, based on the way you have treated me. But I wouldn't do that."
The next day, Trump went on a Twitter tirade, bashing Kelly while alternatively retweeting people who sided with him. Many supporters wrote that they thought the Fox News moderators, Kelly in particular, seemed determined to take down Trump.
In an interview with CNN that week, Trump continued his criticisms of Kelly.
"You could see there was blood coming out of her eyes," he said. "Blood coming out of her wherever."
That remark sparked a firestorm, to which Trump responded by reiterating that his remarks were not problematic, "political correctness" was the problem.
Less than a week later, after receiving an onslaught of online harassment, Kelly took ten days off from her show, The Kelly File. Fox News CEO Roger Ailes released a statement saying that Trump owed Kelly an apology. Trump shot back, saying it was Kelly who should apologize to him.
We "can resolve this now," Ailes said to Trump, according to CNN, "or we can go to war."
Ailes and Trump went on to make peace, with Trump saying that Ailes called him and assured him that he would be treated fairly by the network going forward.
Trump and Kelly's feud has been somewhat reignited by remarks Kelly made in a Vanity Fair profile published online in December.
Kelly said of Trump: "He would send me press clippings about me that he would just sign 'Donald Trump.' And he called from time to time to compliment a segment. I didn't know why he was doing that. And then when he announced that he was running for president, it became more clear. But I can't be wooed. I was never going to love him, and I was never going to hate him."
Trump responded by tweeting: "She is so average in every way, who the hell wants to woo her!"