WASHINGTON — As President Donald Trump and his allies continue to denounce the CIA whistleblower whose complaint led to an impeachment investigation, pressure is building on the spy agency's director, Gina Haspel, to take a stand on the matter, current and former intelligence officials tell NBC News.

"It will be incumbent on her to protect the whistleblower — and by extension, the organization — moving forward," Marc Polymeropoulos, a recently retired CIA officer who oversaw operations in Europe and Russia, said in an interview. "This is a seminal moment for her leadership, and I'm confident she will do the right thing."

So far, Haspel has been publicly silent as Trump has railed about the whistleblower, a CIA analyst, on Twitter. So has the director of national intelligence, Joseph Maguire.

On Wednesday, during Ukraine testimony, the lawyer for Republicans on the House Oversight Committee asked former Ambassador Bill Taylor about an individual who has been identified by some right-wing news organizations as the whistleblower. The president's son Donald Trump Jr. had already tweeted out the same name.

Trump Jr.'s tweet came after Sen. Rand Paul, R-Ky., said Monday he would probably disclose the whistleblower's name, and he urged the news media to do so. Also Monday, the president tweeted: "There is no Whistleblower. There is someone with an agenda against Donald Trump."

Andrew Bakaj, the whistleblower's lead lawyer, has said that disclosure of his client's name would deter future whistleblowers and he has threatened legal action against anyone who reveals the name. In a statement Wednesday, the whistleblower's lawyers said "identifying any suspected name ... will place that individual and their family at risk of serious harm."

The inspector general for the intelligence community, Michael Atkinson, found the whistleblower's complaint about Trump's alleged pressure campaign on Ukraine to be credible. The description of events in the complaint, which has been public for weeks, has largely been confirmed by the transcript of Trump's July phone call with the Ukrainian president and by the publicly available testimony of other witnesses in recent weeks.

Atkinson found that the whistleblower had an arguable political bias, but that it didn't undermine the credibility of his account.

Former CIA Director John Brennan, a Trump critic and NBC News contributor, said intelligence leaders should be pushing back both publicly and privately against what amounts to a campaign to punish the whistleblower.

"Since the affiliation of the whistleblower is unacknowledged, it is up to the Acting DNI Joe McGuire to take a firm public and private stance against any effort to expose the whistleblower," Brennan told NBC News. "Other leaders of the Intelligence Community should privately oppose any attempt to name the whistleblower. Senator Paul's appalling call for the naming of the whistleblower by the media should be denounced in the strongest terms possible; a statement signed by the heads of all the intelligence agencies would be most appropriate."

Another former senior CIA official, who asked not to be named, added, "I think you would have to tell the president we cannot unveil this person — it will create a very bad feeling in the building that will not be good for national security or you personally, Mr. President."

U.S. intelligence officials say they have taken unspecified steps to assure the whistleblower's personal safety, but they have not said whether Haspel or Maguire have urged Trump behind the scenes to stop encouraging efforts to out him.

The law governing intelligence community whistleblowers makes it illegal for the inspector general or others who handled the complaint to reveal his name, but that provision is not binding on others who learn the name outside that formal channel, experts say.

CIA personnel in particular are watching Haspel closely, since the whistleblower is one of their own. That has long been clear, since he first complained to the CIA's general counsel before putting his concerns in writing to the inspector general.

Current and former intelligence officials say Haspel is widely liked and respected within the spy agency, even as she has managed to maintain a cordial relationship with a president who repeatedly has denounced the intelligence community.

Asked why Maguire has not spoken out publicly in response to efforts by Trump and his allies to denounced the whistleblower, a spokeswoman for the acting DNI pointed to his comments when he testified to Congress in September.

"I am committed to ensuring that all whistleblower complaints are handled appropriately and to protecting the rights of whistleblowers," Maguire said. "In this case, the complainant raised a matter with the Intelligence Community Inspector General. The Inspector General is properly protecting the complainant's identity, and we will not permit that complainant to be subject to any retaliation or adverse consequences for communicating the complaint to the IG."

A CIA spokesman said Haspel would have no comment.

"I agree with people who say it's defining moment and I'm confident she'll do the right thing," said Kevin Carroll, a former CIA and Army officer. "She absolutely has a responsibility to stand up for her office."

Some former officers have said that Haspel should resign if Trump names the whistleblower. In 1998, then-CIA Director George Tenet threatened to quit when President Bill Clinton was considering pardoning an Israeli spy, Jonathan Pollard. Clinton backed down.

"Threatening to resign or resigning would be a normal thing for a leader to do in these circumstances," said Larry Pfeiffer, a former senior CIA manager, who noted that he was not saying the whistleblower was a CIA officer. "But in this administration, we seem to see people making the calculation that they can do more to support and help the situation by not resigning."

Some former senior agency leaders told NBC News the risks to the country would be too great if Haspel were to step down and Trump were to appoint a partisan figure to lead the CIA.

"If Trump names the whistleblower, all intelligence community leaders should publicly condemn his blatant disregard of the law and the rights of Intelligence community officials," Brennan said. "They each would need to determine whether their resignation — if Trump didn't fire them first — would be in the best interests of their agency and national security."

Ken Dilanian reported from Washington, and Robert Windrem reported from New York.