Sessions, an early and ardent supporter of U.S. President Donald Trump’s 2016 election campaign, would be the highest government official to testify before the Senate intelligence committee in its probe of allegations that Russia may have sought to interfere in the election.

Democratic Senate leader Chuck Schumer and fellow Democratic Senator Jack Reed questioned on Sunday why Sessions was involved in Trump’s May 9 dismissal of Comey after he had recused himself from investigations of whether Russia meddled in the election, possibly with help from Trump associates.

“There’s a real question of the propriety of the attorney general participating in that in any way, shape or form,” Reed said on “Fox News Sunday.”

Russia has denied interfering in the U.S. election. The White House has denied any collusion with Moscow.

Sessions said in a letter on Saturday that he would appear before the committee to address matters that Comey brought up last week in testimony to the same panel.

He did not say if he would appear in open or closed session. Democrats are pushing for a public hearing. Democratic Senator Ron Wyden, an intelligence committee member, asked the panel’s leaders in a letter on Sunday to hold an open hearing.

A Justice Department official who spoke on condition of anonymity initially said the department expected Sessions to testify in closed session but later stressed that the decision was up to the panel’s Republican chairman, Senator Richard Burr.

A Sessions spokeswoman said she did not know if it would be public. “That’s a question for the committee,” said Justice Department spokeswoman Sarah Isgur Flores.

Republican Senator James Lankford, a member of the intelligence panel, told CBS’ “Face the Nation” the decision was not finalized, but “I assume that this will be public.”

Sessions is skipping a separate hearing on Tuesday on the Justice Department’s budget and sending his deputy for the session that will be open to the public.

Senator Patrick Leahy, the Senate appropriations committee’s top Democrat and a member of the Senate judiciary committee, tartly reminded Sessions that both oversee his department.

“You need to testify before both in public. You can’t run forever,” Leahy tweeted.

Media reports last week said Sessions offered to resign because of tensions with the president over his decision to recuse himself from the FBI’s Russia probe.

Comey accused the Republican president of trying to get him to drop the investigation of former national security adviser Michael Flynn and fired him to undermine the Russia probe.

Trump himself attributed his dismissal of Comey to the Russia investigation.

Comey’s testimony on Thursday also raised new questions about the attorney general’s relationship with Russian officials with ties to President Vladimir Putin. One is whether Sessions had any undisclosed meetings with Ambassador Sergei Kislyak or other Russians during the campaign or after Trump took office.

Sessions in March removed himself from involvement in any probe into alleged Russian election meddling but maintained he did nothing wrong by failing to disclose that he met last year with Russia’s ambassador.

Trump under oath?

Comey’s dramatic testimony drew invective from his former boss on Twitter, with Trump dismissing him as a leaker on Friday and a coward on Sunday.

“I believe the James Comey leaks will be far more prevalent than anyone ever thought possible. Totally illegal? Very ‘cowardly!'” Trump tweeted on Sunday.

The president denied trying to interfere with the investigation and said he would be willing to testify under oath about his interactions with Comey.

“We have to keep in mind that this is one person’s record of what happened. The only two people who know what happened in those meetings are the president and James Comey,” Republican National Committee Chairwoman Ronna McDaniel told Fox.

Schumer invited Trump to testify under oath before the Senate and he urged Trump to produce any tapes of his conversations with Comey. “If there aren’t tapes, he should let that be known. No more game playing,” Schumer said on CBS.

Trump alluded to tapes in a May tweet. Comey welcomed any tapes during his hearing, and congressional investigators have asked the White House to produce them if they exist.

Trump’s tendency to bring up the Russia investigation, whether by insulting Comey or hinting at the existence of tapes, has created a headache for Republicans who want to focus on the party’s priorities such as healthcare and tax reform.

For more about Jeff Sessions, watch Fortune’s video:

Republican Senator Lindsey Graham on Sunday accused Trump of getting in the way of his own agenda.

“You may be the first president in history to go down because you can’t stop inappropriately talking about an investigation that if you just were quiet, would clear you,” Graham said on CBS. “You are your own worst enemy, Mr. President. Knock it off.”