A U.S. official, speaking on condition of anonymity, confirmed on Thursday that an American drone had been shot down by an Iranian surface-to-air missile.

According to the anonymous official, who spoke to the Reuters news agency, the aircraft, a RQ-4A Global Hawk, was flying in international airspace above the Strait of Hormuz when it was shot down.

The statement followed a claim by Iran earlier on Thursday that its Islamic Revolutionary Guard Corps had downed an American drone in Iranian airspace near the Kouhmobarak district in southern Iran’s Hormozgan province, 750 miles southeast of Tehran and close to the Strait of Hormuz.

U.S. Central Command spokesman Capt. Bill Urban disputed the Iranian claim, telling the Associated Press that “no U.S. aircraft were operating in Iranian airspace today,” although he declined to comment when asked if an American aircraft had been shot down.

Last week, the United States alleged that Iran had fired a missile at an American drone responding to an attack on two oil tankers near the Gulf of Oman, an attack that the United States also blames on Iran. Iran has denied responsibility for the incident.

The United States also announced this week that 1,000 additional troops would be deployed to the Middle East, while Iran warned that it would boost its uranium enrichment to weapons-grade levels as the 2015 nuclear deal brokered between the two countries by former U.S. President Barack Obama appears to crumble.