This might be Donald Trump's riskiest move yet. The billionaire is betting that a no-show at the final debate before Iowans caucus on Monday won't hurt his rising poll numbers in the state.

MARSHALLTOWN, Iowa — Moments after Fox News announced the lineup for Thursday's Republican debate, Donald J. Trump said Tuesday it is pretty "irrevocable" that he will skip the event, which takes place just days before the Iowa caucuses.

"Let's see how much money Fox is going to make on the debate without me," Mr. Trump said at a press conference here, where he continued to attack Megyn Kelly and the crew at Fox News, with whom he sparred at an earlier debate.

"It's time that somebody plays grownup," he said. Just after Mr. Trump started speaking, his campaign manager, Corey Lewandowski, confirmed that he will not be attending the debate, saying, "He will not be participating in the Fox News debate on Thursday" and that "it's not under negotiation."

Mr. Trump's absence would leave the main debate stage without the candidate who leads in national polls and has been a big ratings draw for past debates. Mr. Trump has threatened in the past to skip debates, but his remarks Tuesday night were his strongest statement yet that he would not participate.

Trump made the decision shortly after Fox News made public the final lineup for the Des Moines debate, which would have put him at the center of an eight-candidate field.

He said in a statement that he will instead host an event for wounded veterans "who have been treated so horribly by our all talk, no action politicians."

"Like running for office as an extremely successful person, this takes guts and it is the kind mentality our country needs in order to Make America Great Again," he added.

His fight with the network dates to the first GOP debate in August, when Kelly pressed him about questionable remarks he made about women. He told CNN the next day that she was so angry that "you could see there was blood coming out of her eyes, blood coming out of her whatever."

A Fox News spokeswoman said Trump's decision is "rooted in one thing – Megyn Kelly, whom he has viciously attacked since August." He has spent most of the week demanding she be removed as moderator.

"We can’t give in to terrorizations toward any of our employees," said the spokeswoman. "Trump is still welcome at Thursday night’s debate and will be treated fairly, just as he has been during his 132 appearances on FOX News & FOX Business, but he can’t dictate the moderators or the questions.”

There was also a tactical reason for the move. Trump has remained atop the polls despite some rather mediocre debate performances - a sign that his participation doesn't really help him. And skipping this one deprives his top rival, Texas Sen. Ted Cruz, of a chance to assail him in person a last time before voting begins.

Cruz, a one-time college debate champion, quickly invited Trump to a different sort of duel.

Former Gov. Jeb Bush, a frequent target of Trump's attacks at the debate, had reason to celebrate - and find common ground with Georgia pundit Erick Erickson.