The presidential campaigns of GOP candidates Donald Trump and Ben Carson have indicated the candidates plan to boycott the upcoming debate on CNBC, sending a letter to the network listing their demands for rejoining the Oct. 28 event.

Deadline.com reports that the letter requests that the debate run no longer than two hours, including commercial breaks.

“The network also must agree to include opening and closing statements by all candidates on stage, which, in a GOP debate, could mean nearly a dozen statements at each end of the debate,” Deadline reports.

Reps for the two candidates said in the letter to CNBC Washington bureau chief Matthew Cuddy: “Mr. Trump and Dr. Carson do agree to a 120 minute debate that includes commercial breaks and opening and closing statements. Mr. Trump and Dr. Carson do not, and will not, agree to appear at a debate that is more than 120 minutes long including commercial breaks.”

Earlier, Trump went on a Twitter rant against CNBC over the ground rules for the debate.

Among his tweets, Trump wrote: “The @GOP should not agree to the ridiculous debate terms that @CNBC is asking unless there is a major benefit to the party.”

And: “@CNBC is pushing the @GOP around by asking for extra time (and no criteria) in order to sell more commercials.”

His protest followed a conference call between debate organizers and campaign reps in which some of the ground rules were apparently still being hammered out.

“CNBC had no time set aside for the candidates’ opening and closing statements at the debate. Candidates polling in single digits objected, saying it might be the most time they got during the back and forth, according to sources. Trump’s rep supported that concern,” Deadline reports.

In a statement after the conference call, CNBC indicated the format was still being tweaked. “Our goal is to host the most substantive debate possible,” the network said. “Our practice in the past has been to forego opening statements to allow more time to address the critical issues that matter most to the American people. 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.”