President Donald Trump said that a US Navy ship had "destroyed" an Iranian drone in the Strait of Hormuz after the aircraft threatened the ship, in the latest incident in the Gulf.
Mr Trump told an event in the White House that the drone had flown to within 1,000 yards of the USS Boxer.
"This is the latest of many provocative and hostile actions by Iran against vessels operating in international waters. The United States reserves the right to defend our personnel, facilities and interests," Mr Trump said.
"The drone was immediately destroyed," Mr Trump said. He gave no more details.
The Pentagon said in a statement that the USS Boxer, an amphibious assault ship, had taken "defensive action" against a drone, but did not mention if the aircraft was Iranian.
Tensions in the Gulf region are high, with fears that the United States and Iran could stumble into war.
The United States has blamed Iran for a series of attacks since mid-May on shipping around the Strait of Hormuz, the world's most important oil artery. Tehran rejects the allegations.
Earlier today, the United States demanded Iran immediately release a vessel it seized in the Gulf, and a US military commander in the region said the United States would work "aggressively" to ensure free passage of vessels through the vital waterway.