Republican 2016 frontrunners Donald Trump and Ben Carson threatened Thursday to boycott CNBC's presidential primary debate unless it agreed to their terms on the length of the debate and the presence of opening and closing statements.

In a letter, the business mogul and former neurosurgeon say that the network has included terms to which Carson and Trump do not agree.

Specifically the candidates are unhappy with the plan for the debate to over 2 hours, and the decision not to allow 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 commercials breaks. Further, the debate must include opening and closing statements from all the candidates,” the letter to CNBC’s Washington Bureau Chief Matthew Cuddy says.

The letter, sent by both Carson and Trump's camps, says that neither campaign was consulted and says "neither Mr. Trump or Dr. Carson will participate in your debate if it is longer than 120 minutes including commercials and does not include opening and closing statements.”

According to Politico, a number of Republican candidates expressed similar concerns in a conference call with CNBC officials on Wednesday evening.  

Campaign officials from campaigns for Jeb Bush, Chris Christie, John Kasich and Rand Paul were among those who objected to CNBC’s plans for the debate, due to take place on Oct. 28 in Boulder, Colorado.