President Trump said on social media on Tuesday that the U.S. Apache helicopter gunship that crashed off the coast of Oman on Monday night was shot down by Iran and that the United States would retaliate.

“I have just been informed by our Great Military that last night the Iranians shot down one of our highly sophisticated Apache Helicopters while patrolling over the Strait of Hormuz,” Mr. Trump wrote on Truth Social. “There were two pilots involved, both are safe and uninjured. Nevertheless, the United States must, of necessity, respond to this attack.”

The Trump administration had not publicly acknowledged that an Apache went down, with the two crew members safely rescued, until The New York Times reported on the incident on Monday night.

The military’s Central Command confirmed in a statement on Tuesday that an Apache helicopter gunship had gone down on Monday while patrolling regional waters, and that the pilot and gunner were safely rescued within about two hours of the crash. But Central Command did not say how the crash happened and said the incident was under investigation.

Capt. Tim Hawkins, a Central Command spokesman, said in a separate text message that the U.S. Navy deployed a remotely piloted surface drone to help rescue the two crew members.

“The drone picked them up and transported them to another location on the water where they were then hoisted up to a helicopter for further transport,” Captain Hawkins said.

The incident near the Strait of Hormuz occurred after days in which hostilities in the region escalated and then ebbed, as Israel and Iran exchanged military strikes before stepping back, the latest example of the tenuous nature of the cease-fire.