Washington: Republican US presidential frontrunner Donald Trump and the candidate who is hot on his heels on Thursday threatened to boycott their party's next televised debate over its "ridiculous" format.
Trump and Ben Carson wrote to cable broadcaster CNBC, host of the October 28 showdown, to say they were displeased with an agenda recently sent to their campaign teams that explained the debate would last two hours plus four commercial breaks that would add 16 minutes to the format.
In another major change, candidates' opening and closing statements will not be included in the show.
Trump took to Twitter to blast the "ridiculous" format as a way for CNBC to sell more ads.
"Why is the GOP being asked to do a debate that is so much longer than the just-aired and very boring #DemDebate?"
In their letter published by NBC News - NBC Universal owns CNBC - Trump and Carson wrote that neither of the changes were acceptable.
"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."
Trump has dominated the broad Republican field. He leads with 23.4 percent, according to a RealClearPolitics poll average. Carson, a retired neurosurgeon, is second at 19.1 percent.