U.S. President Donald Trump during a closed-door meeting with U.S. diplomats at the Intercontinental Hotel in New York on September 26 accused the whistleblower, who disclosed details of his talk with Ukrainian counterpart Volodymyr Zelensky, of espionage, Bloomberg reported.

"We're at war. These [whistleblowers] are sick people," Trump announced during the meeting, the clip of which first was obtained by Bloomberg.

"I want to know who's the person, who's the person who gave the whistleblower the information? Because that's close to a spy," he said.

"Basically, that person never saw the report, never saw the call, heard something and decided that he or she, or whoever the hell they saw – they're almost a spy," Trump said.

He did not say exactly what he thought the punishment for the whistleblower and his sources should be.

"You know what we used to do in the old days when we were smart? Right? The spies and treason, we used to handle it a little differently than we do now," he said.