A plan to fire live artillery shells over a major Southern California highway as part of a military showcase attended Saturday by Vice President JD Vance drew strong objections from Gov. Gavin Newsom, who said safety concerns forced him to close a portion of the busy interstate.

“The President is putting his ego over responsibility with this disregard for public safety,” the Democratic governor said in a statement. “Firing live rounds over a busy highway isn’t just wrong — it’s dangerous.”

U.S. Marine officials at Camp Pendleton have said there was nothing unsafe about the artillery exercise and no need to disrupt traffic on Interstate 5, which is the main highway along the Pacific coast between San Diego and Los Angeles.

Vance, a Republican, and Defense Secretary Pete Hegseth visited the base in North San Diego County to celebrate the Marine Corps’ 250th anniversary, and watch troops put on a show of amphibious vehicles and Marines demonstrating a beach assault. Vance and his wife, Usha, watched as aircraft shot across the sky and columns of smoke rose from munitions strikes.

The state had considered closing the freeway earlier in the week, but the U.S. Marines said Thursday that the event would occur on approved training ranges and comport with established safety protocols.

State transportation officials ultimately made the decision to close the freeway after practice firings over the freeway Friday evening and a request from event organizers for signage along the road stating “Overhead fire in progress."

The California Highway Patrol closed a 17-mile (27 kilometers) stretch of the highway Saturday. Severe traffic delays were reported Saturday morning and early afternoon in the area around the base.

“This is all because of the White House-directed military event, that for the safety of the public, we need to shut down the freeway since they’re sending live ordinances over the freeway,” California Department of Transportation spokesperson Matt Rocco said.

The California Highway Patrol reopened the I-5 briefly on Saturday afternoon to relieve some of the traffic congestion, Lt. Matt Gutierrez said, but then closed it again.

U.S. Marines Capt. Gregory Dreibelbis said in a statement that there is artillery fire at the base nearly every week and that the exercises didn't endanger motorists.

“Weeks of deliberate planning and rehearsals ensured success at every phase of execution,” he said.

In a statement to The New York Times, a spokesperson for Vance, William Martin, said Newsom misled the public about the safety risk.

"If Gavin Newsom wants to oppose the training exercises that ensure our Armed Forces are the deadliest and most lethal fighting force in the world, then he can go right ahead,” Martin said.

Rocco said the I-5 closure could cost up to another two hours of trip time for those commuting between San Diego and Los Angeles. The freeway carries with 80,000 travelers and $94 million in freight through the corridor daily, according to the governor's office. Passenger rail services running parallel to the I-5 have also been canceled for the afternoon.