Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE and Ben Carson are threatening to skip the next Republican presidential debate unless the format is changed.

The campaigns sent a joint letter Thursday afternoon to CNBC's Washington bureau warning they wouldn't participate in the network’s debate on Oct. 28 in Boulder, Colo., unless it lasts no longer than two hours and includes both opening and closing statements by the candidates.

ADVERTISEMENT

“The criteria that was outlined by CNBC was never discussed with any of the candidates or the campaigns,” Trump campaign manager Corey Lewandowski told The New York Times. “So what CNBC did was send out a memo and said, ‘Here’s the criteria as you have approved them’ and that went out to all the campaigns. We said we never agreed to this criteria.”

NBC News first reported on the joint letter from Carson and Trump.

Ed Brookover, a Carson campaign aide, told The Hill that opening and closing statements are vital to ensuring every candidate is heard on a stage that will likely include 10 candidates. He noted that during one stretch in the last debate, moderated by CNN, Gov. Chris Christie (R-N.J.) went more than 30 minutes without having a chance to speak.

"It's the fairest way to ensure that any candidate has an opportunity to be heard both early and late in the debate and not to rely on the good graces of the moderators," he said.

Trump, meanwhile, was unhappy with the three-hour length of the CNN debate and wants to ensure that the next contest isn't allowed to drag on.

“For us it was imperative that the time be changed to 120 minutes,” Lewandowski told the Times.

“Until we have this criteria specifically laid out, it is difficult to participate.”

Lewandowski has urged the Republican National Committee (RNC) to intervene in the dispute.

Brian Steel, a spokesman for CNBC, told The Hill in a statement that the network typically eschews opening statements "to allow more time to address the critical issues that matter most."

"We started a dialogue yesterday with all of the campaigns involved and we will certainly take the candidates’ views on the format into consideration as we finalize the debate structure," Steel said.

The boycott threat from Trump and Carson, who hold the top two spots in virtually all polling of the Republican race, comes after a handful of other campaigns complained about the debate arrangement on a telephone call with the network and the RNC.

The uproar started, according to one GOP campaign source familiar with the calls, when CNBC told the campaign representatives that there wouldn't be any opening or closing statements for the contest.

"People realized we got the short end of the stick when the Democrats had a 2 minute opening and a 90 second closing [during their debate], so they had three and a half minutes to a 15 million person audience of an infomercial," the source said.

"They get a commercial, we get ‘The Hunger Games.’ "

Representatives from the campaigns of Sen. Ted Cruz Rafael (Ted) Edward CruzTrump argues full Supreme Court needed to settle potential election disputes Press: Notorious RBG vs Notorious GOP The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (R-Texas), Sen. Rand Paul Randal (Rand) Howard PaulSecond GOP senator to quarantine after exposure to coronavirus GOP senator to quarantine after coronavirus exposure The Hill's Morning Report - Sponsored by National Industries for the Blind - Trump seeks to flip 'Rage' narrative; Dems block COVID-19 bill MORE (R-Ky.) and former Florida Gov. Jeb Bush (R) all called for opening and closing statements during the Thursday conference call, according to Politico.

Should Trump and Carson boycott the CNBC debate, the ratings could take a major hit.

The first two Republican presidential debates generated record audiences for both Fox News and CNN, in part due to the presence of Trump, who has added an element of unpredictability to the race.

CNN was reportedly charging more than $150,00 for a 30-second ad during its GOP debate, leading Trump to suggest that the network should send him flowers and a thank-you note.

—This story was last updated at 4:22 p.m.