Lawmakers and the press are seeking answers as the incident has left many wondering about the breadth and depth of the controversy.

The White House has denied that the information in the chat was classified or constituted a 'war plan'.

The conversation, which The Atlantic first published on Wednesday, shows behind-the-scene discussions between Trump's national security team.

But the US national security adviser said he could not explain how a journalist was added to a chat discussing air strikes in Yemen.

President Trump also defended his national security team after a reporter was added to their message thread.

A National Security Council spokesman said in a statement the reported chat "appears to be authentic"

The Signal messages show the inner workings of the president's team and how his Vice-President JD Vance disagreed with him.

The US president says Iran's leadership would be blamed for "every shot fired by the Houthis".