A spokeswoman for the Justice Department declined to comment.
Hogan Gidley, a deputy White House press secretary, said, “The president has nothing but respect for A.G. Barr and greatly appreciates the work he’s done on behalf of the country, and no amount of shady sources with clear intent to divide, smear and slander will change that.”
At various points since the impeachment inquiry began, Mr. Trump has complained that people in his administration have not done more to defend him, multiple people close to the president said. The president’s complaint prompted Mick Mulvaney, the acting White House chief of staff, to try to defend Mr. Trump at an appearance in front of reporters last month.
During that briefing, Mr. Mulvaney initially acknowledged the existence of a quid pro quo linking military assistance for Ukraine to the country’s willingness to start investigations Mr. Trump demanded, before insisting several hours later that he had not said that.
Democratic investigators in the House have spent the past several weeks methodically trying to build a case for impeachment that goes well beyond the July 25 call, interviewing current and former administration officials who have testified to the existence of a shadow diplomatic effort aimed at pressuring Ukraine.
But Mr. Trump’s telephone call with Mr. Zelensky remains the most direct evidence of the president’s involvement. During the call, Mr. Zelensky thanked Mr. Trump for delivering military aid to help in their fight against Russian aggression, including anti-tank weapons.
“I would like you to do us a favor, though,” Mr. Trump responded, shifting the conversation toward investigating Democrats and urging Mr. Zelensky that he work with Mr. Barr and Rudolph W. Giuliani, the president’s personal lawyer.
Mr. Barr has been investigating the origins of the Russia investigation that Mr. Trump has long called “a hoax.” The attorney general appointed the United States attorney John H. Durham to look in to how the Mueller inquiry began and whether the intelligence community did anything improper related to collecting information about the Trump campaign.