New York (CNN) President Trump insulted three reporters affiliated with CNN on Friday, and said the White House may continue to take press passes away from members of the media.

Trump's unprecedented threat poses a serious challenge to the White House press corps and the association that represents them.

At a Q&A session on Friday morning, when a reporter asked Trump, "How long are you going to leave Jim Acosta in the penalty box?," he said "I haven't made that decision, but it could be others also."

Unprompted, Trump brought up April Ryan, the White House correspondent for American Urban Radio Networks, who doubles as a CNN analyst.

"You talk about somebody that's a loser, she doesn't know what the hell she's doing," Trump said. "She gets publicity and then she gets a pay raise or she gets a contract with, I think, CNN." (Ryan has been a regular on CNN for a year and a half.)

"But she's very nasty, and she shouldn't be. She shouldn't be," Trump said. "You've gotta treat the White House and the office of the presidency with respect."

In between his calls for "respect," Trump called Acosta "unprofessional" and disparaged the reporter's intelligence.

Trump also cast doubt on the stated rationale for stripping Acosta's credential.

The White House originally claimed that Acosta placed his hands on an intern who tried to take a microphone from him. Press secretary Sarah Sanders called it "inappropriate behavior." The video proved otherwise. CNN said Sanders' explanation a lie.

On Friday, Trump said of Acosta, "He was not nice to that young woman." But then he said, "I don't hold him for that because it wasn't overly, you know, horrible."

Separately, he called out Acosta's tense exchanges with Sanders at past press briefings, saying "it's a disgrace," suggesting the retaliation was about more than Wednesday's press conference.

CNN has been working behind the scenes on a resolution that would restore Acosta's pass. In the meantime, Acosta has continued to report without physical access to the White House grounds; he is currently in Paris to cover Trump's trip to France.

A number of prominent journalism advocacy groups have come to Acosta's defense and called for an immediate restoration of his press pass.

But some journalists — concerned about which reporter might be targeted next — have been calling for action to match the words. On Friday the Boston Globe's editorial board called for a White House press walkout.

Richard Tofel, the president of ProPublica, tweeted on Friday morning , "What is the plan for when Trump concocts an excuse for vetoing a reporter" from the New York Times or Washington Post? "Surely," he wrote, "we must realize that if it works with CNN, this will just be the first time, and not the last."

CNN's other White House reporters and producers have been unaffected by the action against Acosta. But in effect, the White House is trying to veto Acosta.

"At every good news organization of which I've been aware over 35 years in and around journalism, it has been a bedrock principle that subjects don't get to choose the reporters who cover them, which includes not getting to veto reporters they don't like," Tofel wrote.

At Friday's Q&A session, Trump also had sharp words for CNN White House correspondent Abby Phillip.

She asked one of the day's key questions about newly appointed acting attorney general Matt Whitaker: "Do you want him to rein in Robert Mueller?"

Instead of answering the question, Trump said, "What a stupid question you asked. What a stupid question, and I watch you a lot, and you ask a lot of stupid questions." (Trump has previously said he doesn't watch CNN.)

CNN's Dana Bash tweeted this reaction : "Harvard University will be surprised to hear POTUS call one of their graduates — my friend and colleague Abby Phillip - stupid. In fact she asked THE KEY SMART question: does he want his acting AG to mess with Mueller probe — one he calls a witch hunt."

Phillip and Ryan are two of a small number of African American women who cover the White House. The president has a long history of insulting the intelligence of women and people of color.

Earlier this week Trump snapped at another African American woman, Yamiche Alcindor of PBS, and accused her of asking a "racist question." Her question was about the widespread concerns that Trump's rhetoric emboldens white nationalists.

On Twitter, Astead Wesley of The New York Times connected the dots between the different incidents.

"There are embarrassingly few black and hispanic reporters in the WH press corps and four have been personally insulted by the President this week," he wrote.

After Friday morning's Q&A session, Ryan called into CNN and said she shook off his insults.

A 20-year veteran of the White House beat, Ryan pointed out that each president before Trump "understood that reporters were part of the underpinnings of this nation."

Trump, she said, doesn't seem to appreciate that.