President Donald Trump announced Wednesday that the FAA would order the immediate grounding of all Boeing 737 MAX 8 and MAX 9 aircraft in the U.S., a decision that comes after days of mounting pressure from other countries that left the U.S. as one of the last to make the call after a deadly crash in Ethiopia.

“The safety of the American people, of all people, is our paramount concern,” Trump said, adding that the grounding would take effect as soon as the planes landed and would continue until further notice.

The president said the decision was made based on new evidence that had come to light.

“The FAA is prepared to make an announcement very shortly regarding the new information and physical evidence we’ve received from the site and from other locations and through a couple of other complaints,” he said. “We’ve had a very, very detailed group of people working on the 737 8 and the 737 9 new airplanes. We’re going to be issuing an emergency order of prohibition to ground all flights of the 737 Max 8 and the 737 Max 9 and planes associated with that line.”

But in an important caveat, Trump said the decision to ground the planes “didn’t have to be made” but was made for a number of reasons, he said, including “psychologically and a lot of other ways.”