WATCH: RNC chairwoman gets into testy exchange with reporter over Trump threatening to leave the GOP
Rick Klein and Ronna McDaniel. (Screengrabs)

The chairwoman of the Republican National Committee on Wednesday grew impatient with a reporter on Thursday after being questioned about Donald Trump's commitment to the GOP.

"My colleague Jonathan Karl has a book out this week," ABC News Political Director Rick Klein said at a Christian Science Monitor breakfast.

"In it, he recounts a conversation between you and President Trump where the president, the outgoing president, said he planned to leave the party," Klein noted. "It recounts a scene with you and some of your aides trying to talk him out of it."

In the book, Betrayal: The Final Act of the Trump Show, Karl wrote that the conversation that occurred when McDaniel called to wish Trump farewell during the final hours of his presidency, ABC News reported.

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"I'm done," Trump reportedly told McDaniel. "I'm starting my own party."

"You cannot do that," McDaniel reportedly replied. "If you do, we will lose forever."

"Exactly. You lose forever without me," Trump reportedly shot back. "I don't care."

Klein noted that both the RNC and Trump put out statements denying the report.

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"I just want to be clear, did President Trump have a conversation with you where he said he would leave the party?" Klein asked RNC Chair Ronna Romney McDaniel.

"Listen," McDaniel replied. "President Trump clearly has not left the party."

"And I've never shared my conversations with the president and I'm not about to start doing that now. But I will say one thing that's very true that was said in that statement, which is, if he left the party, we would lose. If he left the party, Republicans would lose," she continued.

Klein was not satisfied with her response.

"You said it was false, the president said it was fake news. What, specifically, was false?" he asked.

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But McDaniel could not explain what in the story was false.

"Did he ever say he would leave?" Klein asked. "Did he tell you that?"

"I've already said I'm not talking about my conversations with the president of the United States.