"I'm not claiming executive privilege, because that's the President's power," Sessions told Sen. Mark Warner, the vice chairman of the Senate intelligence committee.
Instead, Sessions repeatedly said he is "not able to comment" or "not able to discuss" certain topics, citing either Justice Department "longstanding policy," and later, that he is protecting President Donald Trump's right to later on assert executive privilege "if he chooses."
Democrats were unhappy with Sessions declining to testify about his discussions with Trump, citing the longstanding policy.
In a statement issued following the hearing, Sen. Sheldon Whitehouse, the top Democrat on a subcommittee of the Judiciary panel, said: "As someone who served in the Department of Justice, I would love to know what he is talking about."
Sessions' hearing marked the first time the attorney general had testified before Congress since he recused himself from the Justice Department's probe into Russian meddling in last year's election, and since the firing of FBI Director James Comey.
Sessions did not ask the White House about whether Trump was invoking executive privilege over his testimony and Trump did not opt to assert the privilege, a senior administration official said Tuesday. But the same official argued claiming privilege on a hearing without knowing the scope would not comply with "how the process works."
"He didn't ask," the official said, "but going into a hearing and saying we are going to do this ahead of time is not how the process works."
As expected, lawmakers grilled Sessions about his role in Comey's firing, his own involvement in the Trump campaign and his meetings with Sergey Kislyak, the Russian ambassador to the US.
When asked by Sen. Dianne Feinstein about whether he spoke with President Donald Trump about Comey's firing, Sessions said: "I'm not able to discuss or confirm or deny the nature of private conversations that I may have had with the president on this subject or others."
He again cited a Justice Department rule.
"I know how this will be discussed, but that's the rule that's been long adhered to by Department of Justice, as you know, Sen. Feinstein."
The Justice Department did not immediately respond to a request for the DOJ policy Sessions cited during the hearing.
When asked whether this DOJ custom had a written source, a DOJ official pointed CNN to two 1982 memoranda.
"Declining to answer questions at a congressional hearing about confidential conversations with the President is long-standing executive-branch-wide practice," the official said. "The basis for this historical practice is laid out in the 1982 memos from President Reagan and then-Assistant Attorney General Olson."
Sessions time and again Tuesday pointed broadly to historical Justice practices to explain his decision not to answer.
"I am not stonewalling," Sessions told Sen. Ron Wyden. "I'm following historic policies of Department of Justice. You don't walk into any committee meeting and reveal confidential communications with President of United States."
Sen. Martin Heinrich, D-New Mexico, said Sessions' "silence speaks volumes."
"You said you would solemnly swear to tell the truth the whole truth and nothing but the truth," Heinrich told Sessions. "Now you're not answering questions. You are impeding this investigation."
"I'm not able to invoke executive privilege, that's the President's prerogative," Sessions reiterated.
"That's my judgment that it would be inappropriate for me to answer and reveal private conversations with the president when he has not had a full opportunity to review the questions and to make a decision on whether or not to approve such an answer," Sessions said.
This was among the many times Sessions attempted to explain that he is protecting the President's right to choose to invoke executive privilege in not sharing the details of conversations.
"There is no legally binding basis for refusing to answer questions unrelated to an ongoing investigation unless the President is invoking executive privilege," William Yeomans, a 26-year veteran of the Justice Department and fellow at American University Law School, told CNN."That privilege is not absolute -- it can be overcome by a sufficient interest. DOJ traditionally does not discuss ongoing investigations in public, but ultimately must answer questions unless executive privilege is properly invoked and upheld."
The committee can hold Sessions in contempt when he doesn't answer questions -- but that could elongate the testimony and could potentially take months. The committee can also work with the Trump administration to come up with a solution.
"There's no doubt that conversations that involve national security in a real sense are potentially protected by an executive privilege," Diane Marie Amann, a law professor at University of Georgia, told CNN Monday. "But some of the areas that have been under discussion, with regard to confidential communications, are not classified -- and don't implicate national security. That's much more of a gray area."
Sessions said during his hearing he is not sure if he would be able to answer the questions in a closed session.