One official said sailors and marines aboard USS Boxer, a large amphibious assault ship, could see one of the drones go down Thursday. The other drone disappeared from radar and was believed destroyed.
Lt. Col. Earl Brown, a U.S. Central Command spokesman, said: "This was a defensive action by the USS Boxer in response to aggressive interactions by two Iranian UAS (unmanned aircraft systems) platforms in international waters. The Boxer took defensive action and engaged both of these platforms. We observed one UAS crash into the water but did not observe a 'splash' for the other. The United States reserves the right to defend our personnel, facilities, and interests and calls upon all nations to condemn any attempts to disrupt freedom of navigation and global commerce."
Both drones were taken out by a new Marine Corps anti-drone jamming device strapped to the deck—without firing a shot.
Iran has previously denied the claim that a U.S. warship destroyed its drone, releasing on Friday what it said was video proof that the drone had returned to base undamaged.
President Trump on Monday refuted Iran’s claims U.S. forces had not destroyed its drone.
“There's a lot of proof -- it's called take a look at it on the ocean floor. Take your scuba gear and go down there," the president said sitting next to Pakistan’s prime minister Imran Khan in the Oval Office.
Last week, Trump said the USS Boxer took defensive action after an Iranian drone came within 1,000 yards of the warship and ignored multiple calls to stand down.
Trump blamed Iran for a "provocative and hostile" action and said the U.S. responded in self-defense. But Iran's foreign minister, Mohammad Javad Zarif, told reporters as he arrived for a meeting at the United Nations that "we have no information about losing a drone today."
The Iranians and Americans have had close encounters in the Strait of Hormuz in the past, and it's not unprecedented for Iran to fly a drone near a U.S. warship.
The incident last week was the latest in a series of events that raised U.S.-Iran tensions since early May when Washington accused Tehran of threatening U.S. forces and interests in Iraq and in the Gulf.
Fox News' Bradford Betz and The Associated Press contributed to this report.