In a number of testy exchanges with members of the Senate Intelligence Committee, Sessions said he would not answer many of their questions because of a long-standing Justice Department policy that he said protects private conversations between Cabinet secretaries and the president.
The attorney general confirmed elements of Comey's dramatic testimony before the same panel last week while disputing others. Sessions said he was in an Oval Office meeting in February with Comey and Trump when the president said he wanted to speak to Comey privately — and he acknowledged that Comey came to talk to him the next day about the meeting.
At other times, though, Sessions frequently said he couldn't recall specifics, particularly when asked about his meetings with Russian officials during the 2016 campaign.
Above all, Sessions, who served as a senator from Alabama before taking the attorney general post, tried to clear his name and win the sympathy of his former colleagues.
He opened his testimony with a fiery assertion that he never had any conversations with Russians about "any type of interference" in the 2016 presidential election.
"I was your colleague in this body for 20 years," Sessions said. "The suggestion that I participated in any collusion . . . is an appalling and detestable lie."
The attorney general seemed to understand the import of each of his words as the highest-ranking Trump administration official so far to testify publicly on the FBI investigation and Comey's firing. During one line of questioning by Sen. Kamala D. Harris (D-Calif.), he told her in a flash of anger not to rush his answers because "you'll accuse me of lying" and said she was making him "nervous."
Sessions took particular aim at news reports about a possible meeting he had with a Russian official during an April 2016 event at the Mayflower Hotel in Washington, where Trump gave a pro-Russia speech. He acknowledged being at the event and said he had conversations with people there, but did not remember any conversations with Russian Ambassador Sergey Kislyak.
"If any brief interaction occurred in passing with the Russian ambassador during that reception, I do not remember it," Sessions said.
He said that he had met twice with Kislyak — once during the Republican National Convention and once in his Senate office — and that he did not disclose that during his confirmation hearing. He said, however, that he did not remember any other meetings with Russian officials during the 2016 presidential campaign and did not remember any conversations with Russian officials about the Trump campaign.
"Certainly not one thing happened that was improper in any one of those meetings," Sessions said.
When asked to explain why he wrongly claimed in his confirmation hearing that he never met with Russians, Sessions said he was flustered by the question from Sen. Al Franken (D-Minn.) after many hours of testimony.
The attorney general has since recused himself from the Russia investigation — a decision he sought to cast Tuesday as resulting from his role as an adviser on the Trump campaign, rather than because of any inappropriate interaction with Russian officials.
"I recused myself from any investigation into the campaigns for president, but I did not recuse myself from defending my honor against scurrilous and false allegations," he said.
But Sessions's answers seemed to contradict each other at times, particularly when it came to his recusal.
A March 2 email by Sessions's chief of staff said that he would not be involved in "any existing or future investigations of any matters related in any way to the campaigns for the president of the United States." Yet two months later, he played a direct role in Trump's decision to fire Comey, citing Comey's handling of the Hillary Clinton email investigation during the 2016 race.
"The recusal involved one case in the Department of Justice and the FBI,'' said Sessions, referring to the FBI's Russia investigation and offering a different description of the scope of his recusal. "I'm the attorney general of the United States. It's my responsibility to ensure that the department is run properly. I do not believe it is a sound position that if you recuse from a single case, you can't make a decision about the leadership of that agency."
Sessions previously told senators explicitly that he would recuse himself from matters related to Clinton — though Justice Department spokeswoman Sarah Isgur Flores said Tuesday that the case was already closed and therefore not part of the recusal.
When asked about his conversation with Comey on the day the president spoke to Comey alone, Sessions described the exchange differently than the former FBI chief did in his testimony last week.
Comey testified that after what he called a "disturbing" private talk with Trump, he went to Sessions. Without telling the attorney general that Trump had suggested the FBI drop its probe of former national security adviser Michael Flynn, Comey told Sessions, "It can't happen that you get kicked out of the room and the president talks to me.'' The president has denied asking Comey to drop the Flynn matter.
Comey said that the attorney general didn't say anything but that Sessions's body language gave him the sense that he was powerless to do anything.
Sessions said he did respond, telling Comey "that the FBI and the Department of Justice needed to be careful to follow department policies regarding appropriate contact with the White House.''
Sen. Ron Wyden (D-Ore.) suggested that the attorney general was ducking critical questions in his testimony.
"I believe the American people have had it with stonewalling. Americans don't want to hear that answers to relevant questions are privileged or off limits," Wyden said. "We are talking about an attack on our democratic institutions, and stonewalling of any kind is unacceptable."
Sessions shot back: "I am not stonewalling. I am following the historic policies of the Department of Justice."
Wyden noted that Comey had said it was "problematic" for Sessions to oversee the Russia probe, for reasons he did not explain in a public setting.
Sessions became angry again when Wyden pressed him to explain what facts might be "problematic" about his involvement in the probe.
"Why don't you tell me? There are none, Senator Wyden. There are none," Sessions said. "This is a secret innuendo being leaked out there about me, and I don't appreciate it."
Earlier Tuesday, Deputy Attorney General Rod J. Rosenstein appeared before lawmakers on the Senate Appropriations Committee. He responded to questions regarding comments Monday from Christopher Ruddy, the chief executive of Newsmax Media and a friend of Trump, that the president might fire special counsel Robert S. Mueller III. Mueller was recently appointed to lead the investigation into whether the Trump campaign coordinated with Russia to influence the 2016 election.
Rosenstein said that if the president ordered him to fire Mueller, he would comply only if the request was "lawful and appropriate."
Rosenstein, who has been on the job for six weeks, said only he could fire Mueller and only if he found good cause to do so. He described Mueller as operating independently from the Justice Department in his investigation.
Julie Tate and Karoun Demirjian contributed to this report.