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At a joint press conference with Republican leaders at Maryland's Camp David, President Trump responded to criticisms of his mental fitness.

Earlier Saturday, Trump tweeted that his two greatest assets are his "mental stability" and his intelligence. 

Trump took questions from the press while at the presidential compound 20 miles south of Gettysburg, Pa.

Responding to questions about the tweets, Trump pointed out that he graduated from the University of Pennsylvania in West Philadelphia and "made billions" of dollars.

Trump then blasted the author of a new book on the inner workings of his administration, which he said helped lead to such questions about his intellect.

"I hear this guy, that does not know me... [he] didn't interview me. It's in his imagination," Trump said of Michael Wolff.

Trump said that even his critics in the press discredited Wolff's reporting.

"So many of the people I talk about in terms of fake news actually came to the defense of this great administration," he said. "They know [Wolff] and they know he's a fraud."

Trump added that his former confidant Steve Bannon brought the Paterson, N.J. native "into the White House" which resulted in the kerfuffle.

Trump said his mental state is even more validated by the fact he appears to have calmed tensions with North Korean dictator Kim Jong Un for the moment.

The president said Kim is looking to participate in the South Korean-hosted Olympic games this year, and that he views the move as a possible softening of the regime's hardline stand.

"He knows I'm not messing around," Trump said of Kim.

Watch more above.

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