Carla Babb contributed to this report from the Pentagon.
Iran shot down a U.S. drone in an incident Iranian officials said happened over the country's territory but U.S. officials say took place in international airspace.
U.S. Central Command spokesman Capt. Bill Urban said Thursday an Iranian surface-to-air missile shot down a U.S. Navy maritime surveillance aircraft in international airspace over the strait of Hormuz.
He called it an "unprovoked attack on a U.S. surveillance asset," and said the unmanned aircraft is used for intelligence, surveillance and reconnaissance missions over ocean and coastal regions.
In the Iranian account the drone was shot down by the paramilitary Revolutionary Guard in the airspace of the country's southern Hormozgan province, near the Strait of Hormuz.
The U.S. military said Iran tried to shoot down a U.S. drone last week, and tensions between the two countries have increased with attacks against oil tankers in the region that the U.S. blames on Iran, but which Iran says it did not carry out.
Relations have deteriorated since U.S. President Donald Trump withdrew last year from the international agreement that limited Iran's nuclear program in exchange for sanctions relief.
New U.S. sanctions have hurt Iran's economy, and Iran has announced increased production of low-enriched uranium as it seeks help from European nations to circumvent the U.S. measures.