But Democratic senators voiced scepticism about that claim, noting that the journalist, The Atlantic editor-in-chief Jeffrey Goldberg, reported that Defense Secretary Pete Hegseth posted operational details about pending strikes against Yemen’s Houthi militants “including information about targets, weapons the US would be deploying and attack sequencing”.

“We will get the full transcript of this chain, and your testimony will be measured carefully against its content,” he added.

Republican representative Don Bacon, a retired Air Force general who sits on the House Armed Services Committee, told reporters that Hegseth needed to take responsibility for the breach, which he said put lives at risk. Source: AAP / Aaron Schwartz

A former US official told the Reuters news agency that operational details for military actions are typically classified and known to only a few people at the Pentagon.

Classified and sensitive information is not supposed to be shared on commercial mobile phone apps, and unknown numbers – such as Goldberg’s – should not be included.

It remained unclear why the officials chose to chat via Signal rather than the secure government channels typically used for sensitive discussions.