WASHINGTON - Embattled Attorney General Jeff Sessions told the Senate Intelligence Committee on Tuesday that any suggestion that he colluded with Russian officials while he was advising the Trump campaign is "an appalling and detestable lie."

Sessions also said he could “not recall” a third undisclosed meeting with Russian ambassador Sergey Kislyak during an April campaign event.

Sessions said he has never been briefed on the Russia investigation since taking office because he had begun considering his recusal from the Russia matter immediately after taking office.

“I have no knowledge of the investigation beyond what has been reported in the press,’’ Sessions said. “And I don’t even read that.’’

Sessions is testifying in an extraordinary public session in which senators are grilling the nation's chief law enforcement officer on his prior contacts with Russian ambassador Sergey Kislyak and his involvement in the firing of FBI director James Comey.

Sessions testimony comes less than a week after former FBI Director James Comey raised questions about the attorney general’s role in his firing last month and Sessions’ exclusion from a Feb. 14 White House meeting in which Comey was asked to drop the bureau’s investigation into former national security adviser Michael Flynn.

“Attorney General Sessions, this is your opportunity to separate fact from fiction,’’ said committee Chairman Richard Burr, R-N.C.

Burr outlined a slate of questions that lawmakers prepared to pursue, noting that Comey less than a week ago raised questions about the attorney general’s role in his firing last month and Sessions’ exclusion from a Feb. 14 White House meeting in which Comey was asked by President Trump to drop the bureau’s investigation into former national security adviser Michael Flynn.

Comey testified that he decided not to report the president's request to Sessions at the time, because the attorney general was weighing his recusal from all matters related to the Russia investigation — largely for his failure to acknowledge two previous meetings with the Russian ambassador during his January confirmation hearing — and for other “facts’’ the former director said he could not disclose in a public session.

“We also were aware of facts that I can’t discuss in an open setting that would make (Sessions’) continued engagement in a Russia-related investigation problematic,’’ Comey told the Senate Intelligence Committee on Thursday.

Sessions recused himself from the Russia investigation weeks later. The matter that Comey declined to disclose appears to refer to an ongoing inquiry over whether Sessions failed to disclose a third meeting with the Russian ambassador during a April 16 campaign event for then-presidential candidate Trump. Democratic Sens. Patrick Leahy of Vermont and Al Franken of Minnesota had asked the FBI early last year to review the possible third meeting with Kislyak.

"It has been more than three months since the press revealed that the Attorney General gave false testimony in response to questions from me and from Senator Franken about his contacts with Russian officials," Leahy said in a statement Tuesday. "Yet, the Attorney General has made no effort to come back before the Judiciary Committee to explain his actions — actions that could be construed as perjury."

Justice officials have strongly denied that a third meeting occurred between Sessions and Kislyak.

Just hours before Sessions’ appearance, Deputy Attorney General Rod Rosenstein told a separate Senate panel that there was no reason to consider the removal of Russia special counsel Robert Mueller, despite suggestions that Trump was weighing such an action.

“I appointed him; I stand by that decision,’’ Rosenstein told a Senate Appropriations subcommittee. “I will defend the integrity of that investigation.’’

Because Sessions recused himself from all matters related to the investigation, the authority to appoint and remove the special counsel belongs to Rosenstein.

Democrats said Sessions needs to resolve conflicting evidence about contacts with Russians and to explain if and why he recommended Comey's firing by Trump, an action that could be a violation of his recusal.

"The Senate and the American people deserve to know exactly what involvement with the Russia investigation he had before his recusal, what safeguards are in place to prevent his meddling, and why he felt it was appropriate to recommend the firing of Director Comey when he was leading that investigation," said Sen. Charles Schumer of New York, the Senate's top Democrat.

White House spokesman Sean Spicer declined to discuss Trump's "private conversations" with Sessions about Comey, and he left open the possibility that the administration may ask the attorney general to invoke executive privilege regarding them.

"I think it depends on the scope of the questions," Spicer said Monday. "To get into a hypothetical at this point would be premature."

The high-stakes testimony also takes place amid reported friction between Sessions and Trump, who criticized the attorney general's decision to recuse himself from the Russia probe. Sessions reportedly offered to resign in wake of the president's criticism.

Comey's testimony

During his testimony last week, Comey said he had notes of meetings with Trump in which the president asked him for a pledge of personal loyalty and to drop the Russia investigation as it pertained to former national security adviser Flynn. Some Democrats said Trump's actions could amount to an obstruction of justice.

During his testimony, Comey said Trump had specifically excluded Sessions and other top administration officials from the meeting where the president discussed Flynn's possible exposure.

Shortly after the meeting, Comey said he confronted Sessions, saying that had become increasingly uneasy about being left alone with Trump. According to long-standing Justice Department guidelines, contact between the White House and the FBI is supposed to be routed through the attorney general or deputy attorney general to avoid the appearance of undue influence.

Comey said he wrote memos on his meetings with the Trump because of "the nature of the person" he was talking to. "I was honestly concerned that he might lie about the nature of our meeting, and so I thought it really important to document," the ex-FBI director testified.

Trump denied Comey's testimony, saying he never asked the FBI director for a loyalty pledge or to drop the Russia probe. The president said he is willing to testify under oath on these points.

The president and aides noted that Comey testified that he told Trump three times he was not personally under investigation over Russian contacts. They also emphasized Comey's admission that he arranged to have contents of his memos leaked to the news media.

"I believe the James Comey leaks will be far more prevalent than anyone ever thought possible," Trump tweeted over the weekend. "Totally illegal? Very 'cowardly!'"

Contributing: Erin Kelly