The US attorney general, Jeff Sessions, is likely to step into a legal minefield on Tuesday when he answers questions under oath before the Senate intelligence committee about his contacts with Russian officials and his role in the firing of the FBI director, James Comey.

What Sessions tells the committee could in turn affect the legal jeopardy of Donald Trump, who has also said he is willing to speak about his interactions with Comey under oath, although he did not indicate in what forum.

The attorney general – who failed to inform the Senate about his meetings with Russian officials in his confirmation hearings – will face particularly tough questioning from the senators over his apparent role in Comey’s dismissal.

One White House version of events said that Trump fired the FBI director on 9 May after concerns over his performance were raised by Sessions and his deputy, Rod Rosenstein. But Sessions had previously recused himself from matters connected to the Russia investigation, and Comey was overseeing that investigation.

Furthermore, Trump said in a television interview and in an Oval Office conversation with the Russian foreign minister and ambassador the day after Comey’s dismissal that the decision to fire him was linked to that investigation.

“Recommending director Comey’s firing would seem to be a violation of his recusal, and attorney general Sessions needs to answer for that,” the Democratic Senate leader, Chuck Schumer, said in a statement after Sessions’ Senate appearance was confirmed on Monday.

Sessions will be appearing before the intelligence committee five days after Comey’s testimony raised new questions about the attorney general’s role. After Comey’s appearance on Thursday, the justice department put out a statement contradicting the ousted FBI director’s account of an appeal he made to Sessions to make sure he was not left alone with the Trump, who Comey believed was pressuring him to curb the scope of the investigation of contacts between the Trump campaign and Kremlin representatives.

Comey said Sessions did not respond to that appeal. The justice department described the conversation very differently. “Mr Comey said, following a morning threat briefing, that he wanted to ensure he and his FBI staff were following proper communications protocol with the White House,” the statement said.

It insisted that the “attorney general was not silent; he responded to this comment by saying that the FBI and department of justice needed to be careful about following appropriate policies regarding contacts with the White House”.

If Sessions repeats this version of events on Tuesday, he will be testing his credibility against Comey’s. Ryan Goodman, a former Pentagon special counsel, argues that it was a test the attorney general was likely to fail, having previously made statements in the Senate that were proved untrue.

At his confirmation hearing, Sessions volunteered that he had never met with Russian officials during the presidential campaign. He was later allowed to amend the record after press reports that he had met the Russian ambassador, Sergey Kislyak, twice. In the past week, there have been reports of a third meeting.

Goodman argues that the justice department account is unlikely, given that the Comey-Sessions conversation was the day after an extraordinary event, in which Trump ordered other officials, Sessions included, out of the Oval Office, so that he could talk to Comey alone – a violation of White House norms that are supposed to insulate FBI directors from political pressure.

It is increasingly common these days for the administration to include a falsehood in an official statement Former Pentagon special counsel Ryan Goodman

“It is increasingly common these days for the administration to include a falsehood in an official statement,” Goodman wrote on the Just Security blog, which he co-edits. “Repeating that falsehood under oath before Congress is an entirely different matter. It’s a federal crime. And these proceedings have a special counsel looking over them.”

Sessions may seek to invoke executive privilege in discussing his conversations with Trump, and possibly other communications too.

The White House press secretary, Sean Spicer, on Monday did not rule out the possibility of Sessions invoking executive privilege to avoid answering questions about his conversations with Trump relating to Comey. “I think it depends on the scope of the questions,” he said. “To get into a hypothetical at this point would be premature.”

If he does so, a lot will depend on the reaction of the committee’s chairman, Senator Richard Burr.

At a hearing last week in which intelligence officials sought to evade questions, Burr warned them to go back and consult with the White House about their legal position. “At no time should you be in a position to come to Congress without an answer,” the Republican senator said.

Sessions will appear in the Senate well aware he is under scrutiny from the special counsel on the Russia investigation, Robert Mueller, and that anything he says under oath will eventually be compared with Mueller’s conclusions. In his own testimony on Thursday, Comey hinted that Sessions’ involvement in the scandal could be deeper than has been revealed until now.

Explaining why he had left the attorney general out of the loop in discussions about the Russia inquiry, Comey said: “We also were aware of facts that I can’t discuss in an open setting that would make his continued engagement in a Russia-related investigation problematic.”

After Sessions had ducked appearances before other congressional committees, sending Rosenstein in his place, there was some question as to whether he would demand to speak in a closed session of the intelligence committee.

Democrats, led by Senator Ron Wyden, said the session must be open as the matters to be discussed, Wyden said in a letter to Burr, “are directly related to threats to our democratic institutions” and therefore of the “utmost public interest”.

On Monday morning, the justice department said Sessions himself had asked to speak in public.

“He believes it is important for the American people to hear the truth directly from him and looks forward to answering the committee’s questions tomorrow,” it said in a statement.

Additional reporting by David Smith in Washington