WASHINGTON - Senior US national security officials added a prominent journalist to a Signal group chat discussing a military strike on the Houthis in Yemen, making him aware of the airstrike plan two hours before the US operation.

Jeffrey Goldberg, editor-in-chief of The Atlantic, detailed what happened in an article on the magazine's website on Monday. He said that on March 11, he received a connection request on the Signal messaging app from a user named Michael Waltz, which is the name of the US National Security Advisor. But at the time, it was unclear to Goldberg whether this was the official's actual account.

Two days later, Goldberg received a notification that he would be added to a group chat called "Houthi PC Small Group."

A message to the group, from "Michael Waltz," read as follows: "Team - establishing a principles [sic] group for coordination on Houthis, particularly for over the next 72 hours," Goldberg wrote.

The term "principals committee" generally refers to a group of the senior-most national security officials, including the secretaries of defense, state and the treasury, as well as the director of the CIA, he explained.

Goldberg said he had serious doubts about the authenticity of the group chat because he couldn't believe that the US national security leadership would discuss imminent war plans on Signal.

He also couldn't believe that the president's national security advisor would be so reckless as to include the editor-in-chief of The Atlantic in such discussions with senior US officials, including Vice President JD Vance.

However, as the conversation progressed, he began to sense a high degree of verisimilitude.

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"What I will say, in order to illustrate the shocking recklessness of this Signal conversation, is that the Hegseth post contained operational details of forthcoming strikes on Yemen, including information about targets, weapons the US would be deploying, and attack sequencing," Goldberg said, referring to Defense Secretary Pete Hegseth.

After the actual airstrikes happened at the same time as previewed in the group chat, Goldberg reached out to several US officials in the group chat to verify whether this was a genuine Signal thread, and to inquire about why he was added to the chat, among other related questions.

"This appears to be an authentic message chain, and we are reviewing how an inadvertent number was added to the chain," Brian Hughes, the spokesman for the National Security Council, replied.

US President Donald Trump was also asked about the incident by the media at the White House later Monday, and he said that he was unaware of it.

White House press secretary Karoline Leavitt said in a statement, "President Trump continues to have the utmost confidence in his national security team, including National Security Advisor Mike Waltz."

When asked by media about this, Hegseth said, "Nobody was texting war plans. And that's all I have to say about that." The defense secretary also lashed out at Goldberg, calling him "a deceitful and highly discredited so-called 'journalist' who's made a profession of peddling hoaxes time and time again."

The incident sparked grave concerns and harsh criticism.

"If true, this story represents one of the most egregious failures of operational security and common sense I have ever seen," Jack Reed, the Senate Armed Services Committee's top Democrat, said in a statement.

"Military operations need to be handled with utmost discretion, using approved, secure lines of communication, because American lives are on the line. The carelessness shown by President Trump's Cabinet is stunning and dangerous. I will be seeking answers from the administration immediately," said the Democratic senator.

Senate Minority Leader Chuck Schumer described the incident as "amateur behavior" and called for "a full investigation into how this happened and the damage it created."

READ MORE: Death toll from US overnight airstrikes on Yemen rises to 31

"This kind of security breach is how people get killed, how our enemies take advantage, how our national security falls into danger. These people are clearly not up for the job," he posted on social media platform X.