President Donald Trump has downplayed the texting of sensitive plans for a military strike against Yemen's Houthis this month to a group chat that included a journalist, saying it was “the only glitch in two months” of his administration as Democratic lawmakers heaped criticism on the administration for handling highly sensitive information carelessly.

Trump told NBC News that the lapse “turned out not to be a serious one", and expressed his continued support for national security adviser Mike Waltz.

"This certainly, we'll look at this. But the main thing was nothing happened," Trump said. "The attack was totally successful." 

Journalist says he was added in group chat in secure app among Trump officials. – AP

Waltz, according to an article posted online Monday by The Atlantic, appeared to have mistakenly added the magazine's editor-in-chief, Jeffrey Goldberg, to a chat that included 18 senior administration officials discussing planning for the strike.

“Michael Waltz has learned a lesson, and he’s a good man," Trump said.

He also appeared to point blame on an unnamed Waltz aide for Goldberg being added to the chain.

“It was one of Michael’s people on the phone. A staffer had his number on there."

But the use of messaging app Signal to discuss a sensitive operation has opened the administration to blistering criticism from Democratic lawmakers who expressed outrage at the White House's and senior administration officials' insistence that no classified information was shared. Senior administration officials have struggled to explain why the publicly available app was used to discuss such a delicate matter.

Former Pentagon spokesperson speaks out about leaked war plans. – AP

Waltz makes his first public comments

Waltz said Tuesday he was not sure how Goldberg ended up on the chat.

"This one in particular, I’ve never met, don’t know, never communicated with,” Waltz said.

Later Tuesday, Waltz said in an appearance on Fox News that he built the message chain and that White House technical experts were trying to figure out how Goldberg's contact “may have been sucked in”.

“We made a mistake. We’re moving forward," said Waltz, who added that he took “full responsibility” for the episode.

Trump continued to attack The Atlantic and Goldberg and sent mixed messages on whether the administration would change how it goes about sharing sensitive information going forward.

“We won’t be using it very much” in the future, Trump said of Signal.

"That’s one of the prices you pay when you’re not sitting in the Situation Room with no phones on, which is always the best, frankly."

One official reported to be on the Signal chain, Director of National Intelligence Tulsi Gabbard, acknowledged during a Senate Intelligence Committee hearing on Tuesday that she was travelling overseas during the exchange. She wouldn't say whether she was using her personal or government-issued phone because the matter is under review by the White House National Security Council.

US National Security Advisor Mike Waltz. – Reuters

One Democrat calls the mistake ‘an embarrassment’

Both Gabbard and CIA Director John Ratcliffe, who also was a participant in the Signal exchange and also testified at Tuesday's intelligence hearing, faced blistering criticism from lawmakers.

"Director Ratcliffe, this was a huge mistake, correct?” Senator Jon Ossoff, a Georgia Democrat, asked.

After a brief pause, Ratcliffe shook his head. “No,” he said.

Ratcliffe attempted to interject as Ossoff asked a follow-up question, leading the two men to speak over each other.

“This is an embarrassment,” Ossoff said, silencing Ratcliffe. “This is utterly unprofessional. There’s been no apology. There has been no recognition of the gravity of this error.”

Accounts that appeared to represent Vice President JD Vance, US Secretary of State Marco Rubio, Ratcliffe, Gabbard, Treasury Secretary Scott Bessent, White House chief of staff Susie Wiles, and senior National Security Council officials were assembled in the chat group, Goldberg wrote.

Congress reacts to Trump officials texting attack plans with journalist. – AP

In the run-up to his 2016 election victory over Democrat Hillary Clinton, Trump urged criminal prosecution of the former secretary of state for communicating about classified information with her aides on a private email server she set up.

The matter was investigated, but the FBI ultimately recommended against charges. None were brought.

Clinton was among Democrats this week to criticise Trump administration officials' use of Signal.

“You have got to be kidding me,” Clinton said in an online post.

Trump also faced charges for mishandling classified information at his Mar-a-Lago resort following his first White House term. Those charges were later dismissed.

Director of National Intelligence Tulsi Gabbard and CIA Director John Ratcliffe. – Reuters

Administration says Democrats shouldn't be outraged

But on Tuesday, top administration officials were insistent the Democratic outrage was misplaced.

Ratcliffe and Gabbard told lawmakers that no classified information was included in the texts about US attack plans in the message chain.

But The Atlantic reported that the messages included precise information about weapons packages, targets and timing, but did not publish those details.

Pressed on whether such information should be classified, Gabbard hedged. “I defer to the secretary of defence, the National Security Council, on that question,” she said.

Democrats pushed back, saying the leaked military plans show a sloppy disregard for security, but Ratcliffe insisted no rules were violated.

“My communications to be clear in the Signal message group were entirely permissible and lawful and did not include classified information,” Ratcliffe told lawmakers.

The hearing was supposed to be focused on global security threats.

Facing heated questions from Democratic Senator Mark Warner of Virginia, Gabbard said there’s a difference between “inadvertent” releases of information and intentional leaks. “There was no classified material that was shared,” Gabbard said.

Warner, though, said the lapse in security could have cost lives.

“If this information had gotten out, American lives could have been lost. If the Houthis had this information they could reposition their defensive systems,” Warner said.

Trump officials before the Senate Intelligence Committee. – Reuters

Calls for an investigation

In response to questions from Democratic Senator Ron Wyden of Oregon, Gabbard and Ratcliffe said they would participate in an audit looking into administration officials' use of Signal. Wyden said it must be investigated.

“I’m of the view that there ought to be resignations,” Wyden said.

FBI Director Kash Patel, appearing with Ratcliffe and Gabbard at the hearing, said he was only recently briefed on the Signal chat matter and doesn’t have an update on whether the FBI has opened an investigation into it. 

The White House in a statement Tuesday called the uproar a “coordinated effort to distract from the successful actions taken by President Trump and his administration to make America’s enemies pay and keep Americans safe”.

Defense Secretary Pete Hegseth, in his first comments on the matter on Monday, attacked the journalist who received the messages, Goldberg, as “deceitful” and a “discredited so-called journalist” while alluding to previous critical reporting of Trump from the publication.

“Nobody was texting war plans and that’s all I have to say about that,” Hegseth said in an exchange with reporters on Monday at the start of a trip to the Indo-Pacific.

Examining the security of Signal

Signal is an app that can be used for direct messaging and group chats as well as phone and video calls. It uses end-to-end encryption for its messaging and calling services that prevents any third party from viewing conversation content or listening in on calls.

In other words, messages and calls sent on Signal are scrambled – only the sender and recipient at each end will have the key to decipher them.

What is Signal, the chat app used by US officials to share attack plans? – AP

Signal’s encryption protocol is open source, meaning that it’s freely available for anyone to inspect, use or modify. The encryption protocol is also used by another popular chat service, social media company Meta’s WhatsApp platform.

Signal has a "stellar reputation and is widely used and trusted in the security community," said Rocky Cole, whose cybersecurity firm iVerify helps protect smartphone users from hackers.

"The risk of discussing highly sensitive national security information on Signal isn't so much that Signal itself is insecure," Cole added. "It's the fact that nation-states threat actors have a demonstrated ability to remotely compromise the entire mobile phone itself.

"If the phone itself isn't secure, all the Signal messages on that device can be read."

Government officials have used Signal for organisational correspondence, such as scheduling sensitive meetings.

The use of Signal became more prevalent during the last year of the Biden administration after federal law enforcement officials warned that China and Iran were hacking the White House as well as officials in the first Trump administration.

National Security Advisor Michael Waltz with President Donald Trump. – Reuters

Senator Angus King, a Maine Independent, said he was flummoxed by Ratcliffe and Gabbard's assertion that no classified information was included in the chat.

“It’s hard for me to believe that targets and timing and weapons would not have been classified,” he said.

A former US official said operational details for military actions are typically classified and known to only a few people at the Pentagon. Such top secret information is usually kept on computers that use a separate network, the official said.

National Security Council spokesperson Brian Hughes said that the chat group appeared to be authentic. The White House said it was looking into how Goldberg's number was added to the thread.

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.

Asked about the White House claim that no classified details were shared, Bacon responded: "They ought to just be honest and own up to it."