Leading US news outlets have rejected a new Pentagon policy that bars journalists from the building unless they only report information that has been officially authorised by the Department of Defense.

Major outlets, including The New York Times, The Washington Post and CNN, have said they will not agree to the new guidelines, citing concerns it could severely undermine press freedom.

Reporters who do not sign the policy by 17:00 EDT (21:00 GMT) on Tuesday must turn in their media credentials and clear out of the Pentagon facilities, the department has said.

Defence Secretary Pete Hegseth has responded to the backlash from various news outlets on X with a hand-waving emoji, suggesting a goodbye.

The Trump administration argues that the changes are needed to protect national security.

"Pentagon access is a privilege, not a right," Hegseth said on social media. "Credentialed press no longer permitted to solicit criminal acts."

Amemo announcing the changes was sent to reporters last month, telling them that "information must be approved for public release by an appropriate authorising official before it is released, even if it is unclassified".

The Pentagon Press Association has said that most of its members "seem likely to hand over their badges rather than acknowledge a policy that gags Pentagon employees".

"The policy conveys an unprecedented message of intimidation to everyone within the DoD, warning against any unapproved interactions with the press and even suggesting it's criminal to speak without express permission -- which plainly, it is not," the Association said.

More than 100 members have credentials to cover the Pentagon, and for decades reporters with identification badges had unrestricted access to non-classified areas of the building to visit officials.

The Associated Press, Reuters, The Atlantic, The Wall Street Journal and NPR are among the other prominent media organisations with a reporting presence at the Pentagon who have refused to sign the new guidelines.

The major TV networks - ABC News, CBS News, CNN, Fox News Media and NBC News - said in a joint statement that the rules would hinder journalists' ability to "keep the nation and the world informed of important national security issues".

A few right-leaning news organisations, including the Washington Times and Newsmax, have said that their reporters also will not sign the new policy.

The 21-page document lays out a number of requirements, including the provision that military personnel need approval before sharing information with the media, even if it isn't classified.

The policy states that asking agency personnel to "commit criminal acts" by disclosing unauthorised information isn't protected under the First Amendment of the US Constitution that guarantees free speech.

Journalists are technically not barred from reporting or publishing stories on the US military using information deemed unclassified.

But they could be deemed "a security or safety risk" should they disclose classified or even unclassified information under the new rules without the Pentagon's clearance.

"Our policy is also clear: soliciting DOW (Department of War) service members and civilians to commit crimes is strictly prohibited," Sean Parnell, the Pentagon's chief spokesperson, said in a social media post.

"The policy does not ask for them to agree, just to acknowledge that they understand what our policy is," Parnell said on Monday.

Speaking to reporters during a White House meeting on Tuesday, President Donald Trump backed the Pentagon's restrictive new press access rules.

"The press is very dishonest," Trump said, adding, the restrictions were necessary because Hegseth "finds the press to be very disruptive".

"I think it sort of bothers me to have soldiers and, even, you know, high-ranking generals walking around with you guys on their sleeve, asking them, because they can make a mistake and a mistake can be tragic," the president said.

At the same meeting, Hegseth called the restrictions "common-sense stuff" designed to protect classified information and prevent reporters from roaming around the Pentagon.

Rules on press access that were in place at the Pentagon before this new policy had already limited access to restricted areas and classified materials.

The new policy is the latest expansion of restrictions on press access to the Pentagon under Hegseth, a former Fox News host who has rebranded the Department of Defense as the Department of War.

In May, officials removed dedicated Pentagon office space for some outlets, including the New York Times, NBC News, The Hill and CNN.

The spots were allotted instead to the New York Post, One America News Network, Breitbart News Network, HuffPost News and others, in what they called a new rotation programme.

Hegseth has previously come under scrutiny for his own handling of sensitive information after it was revealed he shared details about the bombing of Yemen on a group chat that included a reporter in March.