The Atlantic magazine on Wednesday published what it said was the full text of a chat group mistakenly shared with a journalist by top Trump administration officials laying out plans of an imminent attack on Yemen.
The stunning details, including the times of strikes and types of planes being used, were all laid out in screenshots of the chat.
The magazine said it was publishing after the Trump administration repeatedly denied that any classified information had been included in the unsecure chat.
On Tuesday US President Donald Trump downplayed the scandal but said he would "look into" the use of the Signal app.
He however attacked the journalist Jeffrey Goldberg as a "sleazebag" and said "nobody gives a damn" about the story rocking Washington.
"There was no classified information," Trump told reporters when asked about the chat, saying that the commercial app Signal was used by "a lot of people in government."