(CNN) Once a fixture at the administration's coronavirus briefings, Dr. Deborah Birx has confided to aides and friends that she has become so unhappy with what she sees as her diminished role as coordinator of the White House coronavirus task force that she is not certain how much longer she can serve in her position, sources familiar with her thinking tell CNN.
Birx has told people around her that she is "distressed" with the direction of the task force, describing the situation inside the nation's response to the coronavirus as nightmarish.
According to people familiar with her thinking, Birx views Dr. Scott Atlas, a recent addition to the task force, as an unhealthy influence on President Donald Trump's thinking when it comes to the virus.
"The President has found somebody who matches what he wants to believe," a source close to Birx said of her view of Atlas's relationship with Trump. "There is no doubt that she feels that her role has been diminished."
Birx believes Atlas is feeding the President misleading information about the efficacy of face masks for controlling the spread of the virus, the source said. Trump, whose rallies draw crowds of supporters who refuse to wear masks, has repeatedly mocked Democratic rival Joe Biden for using them.
Speaking from the White House briefing room Wednesday evening, Atlas claimed there isn't any bad blood between himself and Birx.
"Dr. Birx speaks for herself but that's a completely false story and she denied it today. It's completely false," Atlas said at a news conference.
Birx has not yet responded to request for comment on the story, despite Atlas saying she had denied the report.
A White House official rejected the notion that Birx has been diminished in her role on the task force.
"All of the medical experts in the administration are working together around the clock to carry out the President's No. 1 priority: protecting the health and safety of the American people and defeating this virus from China," White House spokesman Judd Deere said. "President Trump relies on the advice and counsel of all of his top health officials every day and any suggestion that their role is being diminished is just false."
A longtime US government health official, Birx became a household name during the early weeks of the pandemic, appearing with Trump at news conferences in the White House briefing room to deliver sobering warnings about the threat posed by the virus. In recent weeks, however, Birx has spent much less time with Trump, as she is now dispatched to raise awareness of the administration's pandemic efforts in states where cases of Covid-19 have surged.
Atlas, a neuroradiologist without expertise in infectious diseases, has seen his prominent role on the task force come under some scrutiny as respected medical experts have questioned his controversial flirtation with "herd immunity" as a solution for the outbreak in the US.
"When you isolate everyone, including all the healthy people, you're prolonging the problem because you're preventing population immunity. Low-risk groups getting the infection is not a problem," Atlas told Fox News in July.
An administration official close to the West Wing's coronavirus response acknowledged the addition of Atlas has unsettled some of the experts on the task force. But the official maintained Atlas "shook things up a bit" and brought "fresh eyes" to discussions behind the scenes, a dynamic Trump prefers.
"He's not been instructed to make friends," the official said of Atlas.
Trump has invited Atlas to appear at recent White House news conferences to field questions from reporters. Noticeably absent in the briefing room are Birx and Dr. Anthony Fauci, the government's leading authority on infectious diseases.
"Don't you think the frustration would be there?" remarked one source close to Birx about the briefings.
The same source said Birx, who has spent much of her career tackling global health crises from Covid-19 to AIDS, is not likely to end her time in government service by stepping down from the task force.
"She is a good soldier. I don't think she's going anywhere," the source said.
Unlike Fauci, who occasionally differs with the President's statements on the virus during television appearances, Birx is seen as much more of a team player inside the administration. During one memorable task force news conference in late April, Birx famously bit her tongue and sat stone-faced as Trump suggested that government researchers investigate whether injections of disinfectants could somehow guard Americans against the virus.
Birx believes her current role as a traveling spokesperson for the administration's coronavirus response in states across much of the south and southwest is having some positive effect, a source said. She has touted the benefits of mask mandates during visits to college towns and other communities where Covid-19 spikes have alarmed local officials.
James Glassman, a friend of Birx and a former top State Department official during the George W. Bush administration, said the task force coordinator is trying to make the best of a difficult situation.
"Dr. Birx is out in the states with the most trouble, telling them the right things about masks and distancing and going back to school," Glassman said. "She's ignoring the nonsense from Scott Atlas and just getting the job done -- just as I've seen her do, fighting AIDS for the past 15 years."
This story has been updated with comments from Scott Atlas.