Journalists at the Pentagon have been told they could be barred if they gather or report information that officials haven't approved first.
Reporters' access to the iconic building, the headquarters of the US defence department, is also being curtailed.
Pete Hegseth, the defence secretary, posted on X: "The 'press' does not run the Pentagon - the people do.
"The press is no longer allowed to roam the halls of a secure facility. Wear a badge and follow the rules - or go home."
A memo announcing the changes was sent to reporters on Friday, informing them "information must be approved for public release by an appropriate authorizing official before it is released, even if it is unclassified".
They must sign an agreement agreeing to the new rules or face having their press pass revoked.