“Let’s be clear, Iran is responsible” for the attacks on U.S. forces, the official said.
American F-16s hit the two locations near Abu Kamal, one of which was a weapons storage area while the other was an ammunition storage area, according to a military official.
It is not yet clear if any Iranians were present at the sites, said the two officials, who spoke on the condition of anonymity to discuss the topic.
American troops have come under attack by a mix of one-way drones and rockets 19 times in Syria and Iraq this month.
Overall, 21 service members have been lightly injured, 19 of which have been diagnosed with traumatic brain injury, the Pentagon confirmed Thursday.
The officials said that the sites were involved in many of those strikes on U.S. troops, and “Iranian fingerprints are all over” the attacks, the defense official said.
“What we did tonight was take a self-defense action because our forces in the Middle East, who are there to support security and stability, are being threatened by Iran, and Iran-backed militias,” the defense official said.
President Joe Biden on Wednesday pledged that the U.S. would respond if the attacks did not stop.
“My warning to the Ayatollah was that if they continue to move against those troops, we will respond, and he should be prepared,” Biden said.
“The President has historically leaned toward restraint, but the recent uptick in attacks forced his hand,” said Jonathan Lord, of the Center for a New American Security.
The Iranian-backed strikes and American response come amid a wider American military buildup in the region in response to the Hamas attack inside Israel, and the Israeli response with thousands of airstrikes inside Gaza.
“The US sent a message tonight that we would directly respond against Iran, and specifically the IRGC, if they continue to attack our military positions and personnel in Syria and Iraq,” said Mick Mulroy, a former Pentagon official and CIA officer. “Iran prefers to hide behind their proxy forces, such as Hamas and Hezbollah, but that will not protect them from responsibility or our retaliation.”
Since the Oct. 7 Hamas attacks, Defense Secretary Lloyd Austin has dispatched several ships, fighter planes and air defenses to the region to help protect American troops, including most recently multiple Patriot battalions and a Terminal High Altitude Area Defense system.
There are about 900 U.S. troops in Syria and another 2,500 in Iraq.
Alex Ward contributed to this report.