The White House vowed on Sunday to fight the news media "tooth and nail" over what it sees as unfair attacks, with a top adviser saying the Trump administration had presented "alternative facts" to counter low inauguration crowd estimates.
On his first full day as president, Trump said he had a "running war" with the media and accused journalists of underestimating the number of people who turned out Friday for his swearing-in.
White House officials made clear no truce was on the horizon on Sunday in television interviews that set a much harsher tone in the traditionally adversarial relationship between the White House and the press corps.
"The point is not the crowd size. The point is the attacks and the attempt to delegitimize this president in one day. And we're not going to sit around and take it," Chief of Staff Reince Priebus said on "Fox News Sunday."
The sparring with the media has dominated Trump's first weekend in office, eclipsing debate over policy and Cabinet appointments.
It was the main theme at the Republican president's first visit to the CIA, at the press secretary's first media briefing and in senior officials' first appearances on the Sunday talk shows.
Together, they made clear the administration will continue to take an aggressive stance with news organizations covering Trump.
"We're going to fight back tooth and nail every day and twice on Sunday," Priebus said.
Aerial photographs showed the crowds were significantly smaller than when Barack Obama took over as president in 2009.
The Washington subway system said it had 193,000 riders by 11 a.m. (1600 GMT) on Friday, compared with 513,000 at that time during the 2009 inauguration.
Spicer's categorical assertion that "this was the largest audience to ever witness an inauguration - period" was widely challenged in media reports citing crowd count experts and was lampooned on social media as well.
Asked on NBC's "Meet the Press" why the press secretary was uttering provable falsehoods, White House senior adviser Kellyanne Conway fired back.
"If we are going to keep referring to our press secretary in those types of terms I think that we are going to rethink our relationship here," she said.
Conway responded to criticism that the new administration was focusing on crowds rather than on significant domestic and foreign policy issues by saying: "We feel compelled to go out and clear the air and put alternative facts out there."
Priebus and Conway focused on a press pool report that said the bust of civil rights icon Martin Luther King Jr. had been removed from the Oval Office after Trump took office. The report on Friday night was quickly corrected, but Trump called out the reporter by name during a visit to the Central Intelligence Agency on Saturday. Spicer also berated the reporter later in the day.
David Maraniss: "Spicer is delivering the most irresponsible, angry & scary statement I've ever heard in WH. They are at war with press. It will not hold."
Glenn Thrush: "Jaw meet floor."
Chuck Todd: "I've run out of adjectives."
Maggie Haberman: "This is not a campaign or an RNC spokesman anymore. Taxpayer-funded briefing room in which several falsehoods told."
A very plugged-in news exec pointed out: "Steve Bannon WANTS a grand divide between Trump and the mainstream media. He wants his world to never trust the media. Maybe this was a win for them."
The Boston Globe's Matt Viser: "The White House is trying to take us into post-factual America. The press, and the public, cannot let that happen."
The Economist's David Rennie: "Why it's alarming Sean Spicer was sent out" to misstate the facts: It "implies his job is to reassure Trump loyalists, not inform USA."
WashPost's Dave Weigel: "The man who forced Spicer to give that statement controls our nuclear arsenal. Enjoy your Saturday!"
NYT's Jonathan Weisman: "I've known Sean Spicer since he was the press aide to the House Budget Committee. I don't know this Sean Spicer."
Toronto Star's Daniel Dale: "Trump's lying has always been a central story. It's not a sideshow, it's the show. Big media still largely unprepared to deal with it."
Mika Brzezinski: "Sean Spicer's first hostage video ... that was pathetic. Embarrassing. Bad. Just bad."
Joe Scarborough: "A president who speaks from hallowed ground at Langley about crowd size and press coverage may soon see his ratings drop into the 20s."