Donald Trump and Ben Carson, the Republicans’ top-polling presidential candidates, threatened to boycott the next GOP debate on CNBC if the format for the event does not change following a chaotic call with the Republican National Committee.

In a joint letter sent to CNBC Thursday, Trump and Carson said they would not participate if the debate ran longer than two hours including commercials or if it did not allow for opening and closing statements by the candidates.

The Republicans’ campaigns discussed the network’s rules on a RNC conference call about the Oct. 28 debate on Wednesday, when Trump’s campaign manager threatened to boycott the event if the demands were not met.

According to Politico’s account of the call – as verified by three unnamed sources – the conversation quickly devolved after two top RNC officials asked for each candidate’s “red line” for circumstances that would force candidates to skip the debate.

A strategist for Sen. Ted Cruz (R-TX) said the candidate might not attend without opening and closing remarks. Rand Paul aide Chris LaCivita responded: “If we don’t have opening and closing statements, CNBC can go fuck themselves.”

Other campaign representatives chimed in, declaring the conference call a “debacle.”

Terry Sullivan, Sen. Marco Rubio’s (R-FL) campaign manager, vowed Rubio would be at CNBC’s debate come “hell or high water.” An adviser to Jeb Bush also said the former Florida governor would attend the event in Boulder, Colo. regardless of the final debate format.

Trump took to Twitter to criticize the “ridiculous debate terms.” He also accused CNBC of “pushing the GOP around” by asking for a longer debate in order to sell more ads.

The @GOP should not agree to the ridiculous debate terms that @CNBC is asking unless there is a major benefit to the party. — Donald J. Trump (@realDonaldTrump) October 15, 2015

Why is the @GOP being asked to do a debate that is so much longer than the just-aired and very boring #DemDebate? — Donald J. Trump (@realDonaldTrump) October 15, 2015

The CNBC debate is slated to include a primetime debate for any candidate polling at 3 percent average between Sept. 17 and Oct. 21, with an undercard debate at 6 p.m. for candidates who don’t make the cut.

Trump has frequently taken credit for pulling viewers to the first two Republican debates on Fox and CNN, both of which delivered record-setting ratings for the networks.

Read the full letter from Trump’s and Carson’s campaigns, obtained by NBC News:

This post has been updated.