Trump says 3rd term isn't a joke, despite term limit

Senate Democratic Leader Chuck Schumer urged Senate Majority Leader John Thune and Senate Republicans to work with Democrats in calling for a "full investigation" into why military operations were coordinated over Signal rather than over taxpayer-funded secure communications channels.

The comments came after The Atlantic reported its editor-in-chief Jeffrey Goldberg was inadvertently added to the chat discussing a U.S. attack on Houthis in Yemen. The White House said the messages appear to be authentic.

"Mr. President, this is one of the most stunning breaches of military intelligence I have read about in a very, very long time," Schumer said on the Senate floor.

"This kind of carelessness is how people get killed. It's how our enemies can take advantage of us. It's how our national security falls into danger," he added.

-ABC News' Isabella Murray

Speaker Mike Johnson downplayed a flurry of national security concerns prompted by The Atlantic's reporting that editor-in-chief Jeffrey Goldberg was added into a Signal group chat discussing classified plans for a strike on Houthi militants.

"The administration is addressing what happened, apparently, an inadvertent phone number made it onto that thread. They're going to track that down and make sure that it doesn't happen again," he said at the U.S. Capitol.

ABC News Correspondent Jay O'Brien pressed Johnson, "But is it irresponsible?"

"Look, I'm not going to characterize what happened," Johnson said. "I think the administration has acknowledged it was a mistake, and they'll tighten up and make sure it doesn't happen again. I don't know what else you can say about."

Johnson added he doesn't believe national security advisor Mike Waltz or Defense Secretary Pete Hegseth should be disciplined for the matter.

President Donald Trump was asked to weigh in on a report from The Atlantic that a Signal group chat discussing a U.S. attack on Houthis in Yemen inadvertently included the outlet's editor-in-chief, Jeffrey Goldberg. White House National Security Council spokesman Brian Hughes shared with ABC News the statement he provided to The Atlantic confirming the veracity of the chat.

"I don't know anything about it. I'm not a big fan of The Atlantic," Trump said.

After a back-and-forth, Trump told the reporter: "I don't know anything about it. You're telling me about it for the first time."

Read more about the messages and the administration's response so far here.

President Donald Trump, alongside Louisiana Gov. Jeff Landry, House Speaker Mike Johnson and Hyundai Executive Chairman Euisun Chung, announced the motor group is investing $5.8 billion in American manufacturing.

"In particular, Hyundai will be building a brand-new steel plant in Louisiana, which will produce more than 2.7 million metric tons of steel a year, creating more than 1,400 jobs for Amesteelworkersorkers," Trump said.

Trump said the investment was "a clear demonstration that tariffs very strongly work."

The president has put tariffs on steel and aluminum products, and is set to implement reciprocal taxes on April 2. Trump said at his event on Monday afternoon that more levies were coming.

"We'll be announcing some additional tariffs over the next few days having to do with automobiles, cars and having also to do a little bit with lumber down the road, lumber and chips," Trump said.