WASHINGTON, United States (AFP) — A US journalist was inadvertently included in a group chat in which Defense Secretary Pete Hegseth, Vice President JD Vance and other top officials discussed upcoming strikes against Yemen's Houthi rebels, the White House confirmed Monday.

President Donald Trump announced the strikes on 15 March, but in a shocking security breach, The Atlantic magazine's editor-in-chief Jeffrey Goldberg wrote that he had hours of advance notice via the group chat on Signal.

"The message thread that was reported appears to be authentic, and we are reviewing how an inadvertent number was added to the chain," National Security Council spokesperson Brian Hughes said.

The White House said Trump "continues to have the utmost confidence in his national security team," after the US president earlier said he did not "know anything about" the issue.

Hegseth, a former Fox News host with no experience running a huge organization like the Pentagon, took no responsibility for the security breach as he spoke to reporters late Monday.

He instead attacked Goldberg and insisted that "nobody was texting war plans," despite the White House confirming the breach.

Goldberg wrote that Hegseth sent information on the strikes, including on "targets, weapons the US would be deploying, and attack sequencing," to the group chat.

"According to the lengthy Hegseth text, the first detonations in Yemen would be felt two hours hence, at 1:45 p.m. eastern time," Goldberg wrote — a timeline that was borne out on the ground in Yemen.

The leak could have been highly damaging if Goldberg had publicized details of the plan in advance, but he did not do so even after the fact.

The journalist said he was added to the group chat two days earlier, and received messages from other top government officials designating representatives who would work on the issue.

On 14 March, a person identified as Vance expressed doubts about carrying out the strikes, saying he hated "bailing Europe out again," as countries there were more affected by Houthi attacks on shipping than the United States.

Group chat contributors identified as National Security Advisor Mike Waltz and Hegseth both sent messages arguing only Washington had the capability to carry out the strikes, with the latter official saying he shared Vance's "loathing of European free-loading. It's PATHETIC."

And a person identified as "S M" — possibly Trump advisor Stephen Miller — argued that "if the US successfully restores freedom of navigation at great cost there needs to be some further economic gain extracted in return."

As he spoke to reporters Monday Hegseth dodged questions about the leak, in which highly sensitive material was not only shared with a reporter but also on a commercial app rather than in secure military channels reserved for such communications.