Top Trump administration officials mistakenly texted secret war plans to a journalist in one of the most “stunning” breaches of military intelligence.

The Atlantic editor-in-chief Jeffrey Goldberg revealed he was inadvertently invited to a messaging group discussing highly classified details about military strikes in Yemen.

The encrypted chat group on the Signal messaging app included US Vice President JD Vance and Secretary of Defence Pete Hegseth.

“The world found out shortly before 2pm eastern time on March 15 that the United States was bombing Houthi targets across Yemen,” Goldberg wrote in the magazine.

“I, however, knew two hours before the first bombs exploded that the attack might be coming. The reason I knew this is that Pete Hegseth, the secretary of defence, had texted me the war plan at 11.44am.”

Messages in the group included US national security adviser Mike Waltz asking his deputy Alex Wong to set up a “tiger team” to co-ordinate US action against the Iran-backed Houthis.

Democratic lawmakers called the use of the Signal group illegal and demanded an investigation.

“This is one of the most stunning breaches of military intelligence that I have read about in a very, very long time,” Senate Democratic Leader Chuck Schumer said, adding that he would ask Majority Leader John Thune to investigate.

One of the messages Goldberg says he was sent.

The US has conducted airstrikes against the Houthis since the militant group began targeting commercial and military vessels in the Red Sea in November 2023.

Hours before the attacks, Hegseth posted operational details about the plan, “including information about targets, weapons the US would be deploying, and attack sequencing”, Goldberg said.

He declined to disclose the details of what he termed the “shockingly reckless” use of the Signal chat to co-ordinate the strike.

Goldberg said he didn’t think the group was real at first.

“I could not believe that the national-security leadership of the United States would communicate on Signal about imminent war plans,” he said.

He also said he “could not believe that the national security adviser to the President would be so reckless as to include him in the discussions with senior US officials”.

“I have never seen a breach quite like this,” Goldberg wrote.

He ultimately notified the White House about the security breach and removed himself from the chat.

Hegseth denied sharing war plans in the group chat.

“Nobody was texting war plans, and that’s all I have to say about that,” he said while on an official trip to Hawaii.

A second message sent to Goldberg.

According to screenshots of the chat reported by The Atlantic, officials in the group debated whether the US should carry out the strikes. At one point, Vance appeared to question whether US allies in Europe, more exposed to shipping disruption in the region, deserved US help.

“Pete Hegseth, if you think we should do it, let’s go,” a person identified as Vance wrote.

“I just hate bailing Europe out again,” the person wrote, adding: “Let’s just make sure our messaging is tight here.”

A person identified as Hegseth replied: “VP: I fully share your loathing of European free-loading. It’s PATHETIC.”

The information leak has been condemned by former US security advisers.

“Dear Sweet Baby Jesus,” one former senior US official told CNN when the reporting was revealed.

Another former senior official said:

“They broke every procedure known to man about protecting operational material before a military strike … You have a total breakdown in security about a military operation.”

“We’re just finding out about it. But obviously, we’ve got to run it to ground and figure out what went on there. We’ll have a plan,” said Thune, a Republican from South Dakota.

Democratic Senator Elizabeth Warren said on X the use of Signal to discuss highly sensitive national security issues was “blatantly illegal and dangerous beyond belief”.

President Donald Trump was asked about the leak during a White House event.

“I don’t know anything about it,” Trump began, before taking a swipe at the magazine.

“I’m not a big fan of The Atlantic. To me, it’s a magazine that’s going out of business. I think it’s not much of a magazine, but I know nothing about it.”

The development came just after Hegseth’s office announced a crackdown on leaks of sensitive information. It has also floated using polygraphs on defence personnel to determine where leaks are coming from.

The Defence Department referred a Reuters request for comment to the National Security Council, and NSC spokesman Brian Hughes said the chat group appeared to be authentic.

“At this time, the message thread that was reported appears to be authentic, and we are reviewing how an inadvertent number was added to the chain,” he said.

“The thread is a demonstration of the deep and thoughtful policy co-ordination between senior officials. The ongoing success of the Houthi operation demonstrates that there were no threats to our servicemembers or our national security,” Hughes said.

-with AAP