The Senate Intelligence Committee hearing was nominally about an annual report on national security threats, but Democrats used the opportunity to hammer officials -- two of whom were reported to be in the group chat -- over the mounting row.

Pressed by Democratic Vice Chair Mark Warner over how military plans could be posted in Signal, a publicly-available instant messaging app known for its encryption, Director of National Intelligence Tulsi Gabbard repeatedly denied that classified material had been shared.

But she refused to go into further detail or confirm her presence in the group.

Warner criticized her reticence and urged her to share the content of the chat, if indeed no classified information had been divulged.

The breach was revealed Monday in an article by Jeffrey Goldberg, editor in chief of The Atlantic magazine, who said he had given detailed plans on rebel Huthi targets in Yemen just hours before they were launched.

Others in the chat appeared to include Vice President JD Vance and Defense Secretary Pete Hegseth, as well as National Security Advisor Mike Waltz.

Goldberg was initially skeptical but said he realized the chat was real when reports of strikes in Yemen emerged on the timeline that had been shared in the group, and at that point left.

He chose not to reveal the contents of all the messages for fear of compromising security and potentially endangering American forces in the Middle East.

But the existence of a group in which top Trump officials were discussing military planning in an unofficial chat app has raised widespread concerns about managing sensitive intelligence.

The White House confirmed the authenticity of the group chat, but also asserted that no classified information had been revealed.

Unlike Gabbard, CIA chief John Ratcliffe confirmed his presence in the chat to senators Tuesday, but defended the decision to use Signal for the discussion.

Warner appeared unconvinced.

"If this was the case of a military officer or an intelligence officer and they had this kind of behavior, they would be fired," he said, branding the incident "one more example of the kind of sloppy, careless, incompetent behavior, particularly towards classified information."

Democratic Senator Ron Wyden called for the resignations of Waltz and Hegseth.

The former is said to have been behind the inadvertent addition of Goldberg into the group, while the latter is said to have shared the plans for the strikes on the Huthis.