U.S. Attorney General Jeff Sessions on Tuesday denied having an undisclosed meeting with Russia's ambassador to Washington or improper communications with other foreign officials, saying the notion that he colluded with Russian officials during last year's presidential election was an "appalling and detestable lie."

In a heated testimony before the Senate Intelligence Committee investigating Russian meddling in the election, Sessions, who was an adviser to President Donald Trump's 2016 president campaign, said he met twice with Russian Ambassador Sergey Kislyak last year, but he denied reports that he had a third undisclosed meeting with Kislyak at a Washington hotel last April.

Sessions Denies Improper Contacts With Russians

"Let me state this clearly: I have never met with or had any conversations with any Russians or any foreign officials concerning any type of interference with any campaign or election," Sessions said.

Sessions Denies Improper Contacts With Russians

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Sessions Denies Improper Contacts With Russians

But Sessions frequently framed his answers with "to the best of my knowledge" qualifiers and left open the possibility that he had a casual encounter with Kislyak at a reception preceding a foreign policy speech by Trump at the Washington Mayflower Hotel.

"If any brief interaction occurred in passing with the Russian ambassador during that reception, I do not remember it," Sessions said.

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The testimony, Sessions' first since he recused himself from oversight of the Russia probe in March following reports of his meetings with Kislyak, came after new reports that the former senator may have had a third undisclosed meeting with the Russian diplomat.

Going into the testimony, Sessions said he wanted to address questions raised by ousted FBI Director James Comey during his testimony before the same panel last week.

A Sessions spokeswoman later said the attorney general had requested the meeting be open, adding that he looked "forward to answering the committee's questions."

But Tuesday's hearing grew testy as Sessions refused to answer questions about his conversations with Trump, drawing charges of stonewalling from Democrats on the panel.

Asked by Democratic Senator Dianne Feinstein if he had discussed Comey's handling of the Russia investigation with Trump or any other official, Sessions said, "I'm not able to comment on that."

Asked by Republican Senator Marco Rubio about a February 14 Oval Office with Trump, Sessions responded, "That's a communication in the White House that I'd not comment on."

In dodging questions about his private conversations with Trump, Sessions invoked a “long-standing” Department of Justice policy of not commenting on confidential conversations between the attorney general and the president rather than executive privilege.

Republican Senator James Lankford of Oklahoma defended Sessions' reticence, arguing that Obama administration officials had similarly withheld information, but Democrats were infuriated.

"You raised your right hand here today and said you would solemnly swear to tell the truth, the whole truth and nothing but the truth," Democratic Senator Martin Heinrich of New Mexico said. "Now you're not answering questions. You're impeding this investigation."

Former Department of Justice officials said they were not aware of such a policy.

"If there is a long-standing Department of Justice policy requiring it, I'm unfamiliar with that policy," said David Sklansky, a former federal prosecutor who is now a professor at Stanford University Law School.

Laurie Levenson, another former Department of Justice official, said she was unfamiliar with the policy, saying, "There has to be follow-up by Congress."

Sessions appeared before the intelligence committee five days after Comey, the former FBI director, delivered a dramatic testimony of his own before the same panel, accusing Trump of initiating improper one-on-one communications with him and trying to get him to drop an investigation into former National Security Advisor Michael Flynn.

Comey testified that he later voiced concern about his meeting with Trump to Sessions, but that Sessions failed to respond.

Sessions corroborated Comey's account, but he said he saw “nothing improper” for the president to meet alone with the FBI director and that he advised him to follow Department of Justice protocols in communicating with the White House and the president.