The White House has limited the number of people allowed to listen to calls between President Trump and foreign heads of state, according to CNN.

"Nobody is allowed on the calls," a source told CNN. "The barn door officially closed after the horse escaped," the source also said in reference to the July 25 call between Trump and Ukrainian President Volodymyr Zelensky. The phone call and subsequent leaked content has been the crux of the impeachment efforts by the Democrats against Trump.

Trump is reportedly limiting his call-sharing to a minimum of qualified staff including national security adviser Robert O'Brien, who will approve everyone who participates in the calls.