Trump has faced criticism ever since putting Whitaker in charge without getting Senate approval for him.
The temporary appointment also sparked worries that Whitaker would hamstring or even kill the ongoing investigation by special counsel Robert Muller into Russian interference in the 2016 presidential election and possible collusion by Trump's campaign.
Trump has repeatedly railed against that probe — most recently in a storm of angry tweets Friday morning. Trump had long been angry at Sessions for the appointment of Mueller as special counsel, which was set in motion when Sessions recused himself from the Russia investigation because of his own contacts with Russians during the presidential campaign.
Trump told reporters that he "did not know" Barr until recently, "when I went through the process of looking at people."
"He was my first choice, from day one, respected by Republicans, and respected by Democrats," Trump said. "He will be nominated for the United States attorney general, and hopefully that process will go very quickly and I think it will go very quickly."
"I've seen very good things about him, even over the last day or so when people thought [Trump's AG nominee] would be Bill Barr."
Barr, who was last attorney general from 1991 to 1993, currently is of counsel in the Washington office of the high-powered Kirkland & Ellis law firm.
A year ago, when The New York Times reported on Trump's call for the Justice Department to investigate supposed wrongdoing by 2016 Democratic presidential nominee Hillary Clinton, Barr said, "There is nothing inherently wrong about a president calling for an investigation."
"Although an investigation shouldn't be launched just because a president wants it, the ultimate question is whether the matter warrants investigation," Barr told the newspaper.
The Times reported at the time that Barr saw more reason to investigate Clinton's purported role in signing off on the purchase by Russia's atomic energy agency of a Canadian firm which holds a significant chunk of U.S. uranium production capacity than there was to probe possible coordination between the Trump campaign and Russia.
Barr also told told The Washington Post in November 2018 that, "I don't think all this stuff about throwing [Clinton] in jail or jumping to the conclusion that she should be prosecuted is appropriate."
"But I do think that there are things that should be investigated that haven't been investigated," he said.
In 2017, Barr was asked by the Post about Trump's claims that Mueller's team of prosecutors is biased because some of them had contributed to political campaigns of Democrats.
"In my view, prosecutors who make political contributions are identifying fairly strongly with a political party," he told the Post. "I would have liked to see him have more balance on this group."
Barr served in the CIA from 1973 through 1977. He later was on the White House domestic policy staff during the Reagan administration. He became an assistant attorney general in 1989.
After leaving the attorney general's post in 1993, Barr spent more than 14 years in top corporate legal positions, including as general counsel and executive vice president of Verizon Communications. He retired from Verizon in 2008.