Trump's firing of Atkinson led to bipartisan concerns in Congress, with a group of eight senators led by Sen. Chuck Grassley (R-Iowa) writing to Trump on Wednesday demanding further explanation of Atkinson's firing.

Trump said in his initial letter expressing his intent to fire Atkinson that he no longer had the president's "fullest confidence" — an explanation the senators found insufficient.

During his interview with Ingraham, Barr said he felt Atkinson had gone beyond his authority in notifying Congress of the then-reported contacts between Trump and Zelensky.

"He was obliged to follow the interpretation of the Department of Justice and he ignored it," Barr said. "I think a president was correct in firing him."

Trump was impeached for abuse of power and obstructing Congress in its investigation after pressuring Zelensky into launching a public investigation designed to damage Democratic presidential candidate Joe Biden.

Barr has repeatedly come to Trump's defense on Ukraine and the Russia scandals, and in October 2019 opened a criminal investigation into the FBI's own Russia investigation for possible abuse or improprieties. The U.S. attorney for Connecticut, John Durham, heads that investigation.

Barr wouldn’t tell Ingraham how far Durham had advanced in the investigation, but said it was a “sprawling case” that “takes some time” to fully investigate.

"I think a report may be and probably will be a byproduct of his activity but his primary focus isn't to prepare a report. He is looking to bring to justice people who were engaged in abuses if he can show that they were criminal violations and that's what the focus is on," Barr told Ingraham.

Trump's allies are hoping any report from Durham’s investigation would serve as a counter to the long trail of scrutiny around the 2016 election.

Barr argued that the FBI investigation into Trump's presidential campaign was riddled with abuse of power and had no evidence to back it up. He did not mention the intelligence that prompted the investigation, including a Trump campaign adviser boasting that he knew Russia had damaging information on then-Democratic candidate Hillary Clinton.

"I think the president has every right to be frustrated because I think what happened to him was one of the greatest travesties in American history," Barr said. "Without any basis, they started this investigation of his campaign and even more concerning actually is what happened after the campaign, a whole pattern of events while he was president."