UPDATE: CNBC agreed Friday to Trump's demand that the debate be two hours and include opening and closing statements.

Donald Trump went "On The Record" tonight and wouldn't commit to attending the next Republican presidential debate unless CNBC makes changes to the debate format.

Several campaigns are unhappy with the criteria that have been set by CNBC, including the lack of opening and closing statements, and the lack of a set length of time for the Oct. 28 debate, which will take place at the Coors Events Center in Boulder, Colorado.

Trump told Greta Van Susteren that CNBC has sold out all their commercials, so they want to increase the length of the debate by an hour to make more money.

"The Democratic debate, if you look at it, that was two hours, and it was too long. Everybody was bored at the end. They want to make this much longer than that," Trump said. "So I think it's really important that they make it a reasonable period of time."

"The networks are making a fortune off this stuff," Trump said. "I wonder why."

Greta said she took Trump's comments to mean that he will still attend the debate if it's three hours, but he's pushing hard for it to only be two.

Watch more from "On The Record" above.

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