From left: Acting FBI Director Andrew McCabe, Deputy Attorney General Rod Rosenstein, Director of National Intelligence Dan Coats, and National Security Agency Director Michael Rogers. Aaron P. Bernstein/Reuters WASHINGTON — At the Senate Intelligence Committee's open hearing on Wednesday with top intelligence officials to discuss Foreign Intelligence Surveillance Act legislation, lawmakers homed in on the circumstances surrounding the firing of James Comey as FBI director.

Democratic Sen. Mark Warner told the witnesses — National Security Agency Director Adm. Mike Rogers, acting FBI Director Andrew McCabe, Deputy Attorney General Rod Rosenstein, and Director of National Intelligence Dan Coats — that it was "jarring" to hear "recent reports of White House officials, perhaps even the president himself, attempting to influence and enlist our intelligence-community leaders in attempting to undermine an ongoing FBI investigation."

The Washington Post reported on Tuesday that Trump had asked Coats how he could prevent Comey from investigating his former national security adviser, Michael Flynn, over his ties to Russia. Trump fired Comey on May 9, amid the FBI's probe into Russian election interference and whether Trump's campaign colluded with Moscow during the election.

"If any of this is true, it would be an appalling and improper use of our intelligence professionals — an act that could erode the public's confidence in our intelligence institutions," Warner said. "The [intelligence community] fiercely prides itself on its apolitical service to the country. Any attempt by the White House or even the president himself to exploit this community as a tool for political purposes is deeply, deeply troubling."

Warner asked Rogers whether he thought it was typical for a president to discuss with top intelligence officials an ongoing FBI investigation that could concern his campaign.

Rogers replied that he could not discuss specifics, but that in his more than three years as the NSA's director, he had never felt "pressured" to intervene in or alter the course of an investigation. He added that he had never been directed to do anything "immoral" or "illegal."

McCabe, Rosenstein, and Coats. Kevin Lamarque/Reuters

Coats similarly said he did not feel it would be appropriate to address "confidential information" about his conversations with Trump in a public setting. About the Post report, Coats would not mention Trump by name but said he had "never felt pressured" by anyone "to intervene or interfere in any way to shape intelligence" in an ongoing investigation.

Warner replied that if Trump was "even asking," however, "that is very relevant."

"At some point, these facts have to come out," he added.

Sen. Marco Rubio chimed in later, saying he thought that if what was being said in the media was untrue, "then it is unfair to the president," but otherwise, the American people needed to know.

Coats replied that he was willing to come before the committee "to tell you what I know and don't know," but that he was "not prepared to answer your question" in an open hearing. Rubio said he was not asking for classified information, but Coats insisted he would "not go down that road in a public forum."

Rogers echoed Coats' statement. McCabe and Rosenstein said they were not aware of anyone receiving a call from the president or his allies asking how they could intervene in any ongoing investigations.

Democratic Sen. Ron Wyden asked the witnesses whether they had taken notes or recorded any of their conversations with the president that concerned the Russia investigation, as Comey reportedly did. None would comment.

Independent Sen. Angus King aggressively questioned McCabe and Rogers, asking for a legal justification for why they could not discuss whether the president asked Comey to back off the Russia investigation.

Both McCabe and Rogers replied that they did not "feel it would be appropriate" to comment on something that may fall under the purview of the FBI's special counsel, Robert Mueller.

"What you feel isn't relevant, admiral," King told Rogers.

Warner later said that if Mueller had instructed the witnesses not to answer the questions, then the American public deserved to know.

"We have gotten no answer from any of you," Warner said.

Republican Sen. John McCain asked Coats whether he would be willing to discuss in a private session the Post report that said Trump had asked him how he could stop Comey from investigating Flynn. Coats indicated that he would, before saying that "not everything" printed in The Post should be taken "at face value."

Warner still appeared frustrated at the end of the session, telling the panel that he would come out of the hearing "with more questions than when I came in."

He said that while the officials had indicated a commitment to not getting in the way of Mueller's investigation, "we don't seem to have the same commitment from you to finding out whether the president tried to intervene directly with leaders of the intelligence community" to influence the Russia probe.

Warner said that what Trump discussed with the witnesses was "absolutely critical."

"The president is not above the law," he said.