"When you call a foreign leader, people listen. I may end the practice entirely, I may end it entirely," Trump said in an interview with Geraldo Rivera.

Trump has repeatedly cited how many people were on his July 25 call with Ukrainian President Volodymyr Zelensky as a justification for why he would not have acted improperly by asking for investigations into the Biden family or a baseless theory that Ukraine interfered in the 2016 election.

But in recent weeks he has become preoccupied with the idea that someone could leak what he says on a future call with a foreign leader, sources familiar tell CNN.

Calls with world leaders are highly coordinated events that in the past have required careful planning by the President's national security team. During a typical call between a US president and a foreign leader, dozens of officials can join the call. Some are in the room with the President, such as the national security adviser or secretary of state, but many listen from remote locations or the Situation Room. Trump has developed a habit of calling world leaders from the White House residence.

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