The amphibious assault ship USS Boxer performs maneuvers off the coast of Southern California in this Dec. 6, 2008 file photo. (Xinhua/REUTERS)

WASHINGTON, July 19 (Xinhua) -- U.S. President Donald Trump confirmed Friday that an Iranian drone had been destroyed by a U.S. warship, while Tehran denied the U.S. assertion.

"No doubt about it ... we shot it down," Trump replied to reporters in the Oval Office when asked to confirm the downing of the Iranian drone.

U.S. National Security Adviser John Bolton, who was also on the scene, added that "there is no question" that it was an Iranian drone and USS Boxer took it out.

Trump announced on Thursday that USS Boxer, an amphibious assault ship, destroyed the drone over the Strait of Hormuz, calling the downing "defensive action."

The drone was flying within 1,000 yards of the U.S. warship and ignored multiple warnings, Trump said.

Iran, however, rejected the U.S. claim. "We have not lost any drone in the Strait of Hormuz nor anywhere else," Abbas Araqchi, the Iranian deputy foreign minister, said in a tweet late Thursday.

"I am worried that USS Boxer has shot down their own UAS (unmanned aerial system) by mistake," he said.

Iran's Islamic Revolution Guards Corps (IRGC) on Friday announced that it had seized the British oil tanker, Stena Impero, in the Strait of Hormuz, saying the vessel failed to respect the international maritime rules while passing through the strait.

The downing of the Iranian drone came one month after a U.S. drone operating over the Strait of Hormuz was shot down by Iranian air defense system on June 19, which almost led to a U.S. military retaliation against Iran.