Incurable 'gossip' Trump won't be able to resist selling classified info after leaving office: MSNBC's Mika
President Donald Trump meets with Russian Ambassador Sergey Kislyak (Photo via Twitter).

MSNBC's Mika Brzezinski knows President Donald Trump, and she knows that he likes to gossip.

The "Morning Joe" co-host says there's no doubt that Trump will reveal some of the top-secret information he's learned as president once he leaves the White House, and she said that presents an unprecedented threat to national security.

"He doesn't keep secrets," Brzezinski said. "He can't, he doesn't know how. He loves to sort of revel in knowing things and passing it along. His personality seems to be 100 percent undisciplined."

Making matters worse, that information could be extremely valuable.

"I do think that this president, this man, has the, not just the ability, but the No. 1 self-focus to use everything that he has in his possession for his financial gain," Brzezinski said. "So it's not just sharing information right now with the Biden, with the Biden team, and creating a proper transition, which should be happening -- and thank God, Joe Biden knows where the bathroom is. He knows where all of the -- everything -- how the White House works, so a transition will not be as difficult for a Joe Biden."

"But when it comes to classified information and relationships with foreign adversaries and friends that need to be had, this is dangerous," she added, "and I worry that Donald Trump takes information out of the White House, and I don't know if we have seen someone who wants to abuse information that he took in while in office, but he will."

Co-host Willie Geist agreed that this president would not be able to resist his impulse to blab, especially when there's potential monetary rewards for his gossip.

"I think you're right to go back to his pre-presidency and his personality, which is that he likes to be the guy with the information," Geist said. "It was gossip back then, now it's national security secrets. Go back to sitting out on the patio at Mar-A-Lago with Shinzo Abe when news of the North Korea missile test came out, and he shared that not only with the prime minister, but with the membership dining at tables around him. You're right to be worried about that."