The United States launched airstrikes in Syria today, targeting facilities near the Iraqi border used by Iranian-backed militia groups.
The Pentagon said the strikes were retaliation for a rocket attack in Iraq earlier this month that killed one civilian contractor and wounded a US service member and other coalition troops.
American officials said the attack killed a "handful" of militia, but the Pentagon did not provide any detailed assessment of the damage.
The airstrike was the first military action undertaken by the Biden administration, which in its first weeks has emphasised its intent to put more focus on the challenges posed by China, even as Mideast threats persist.
"This proportionate military response was conducted together with diplomatic measures, including consultation with coalition partners," the Pentagon's chief spokesperson, John Kirby, said in announcing the strikes.
"The operation sends an unambiguous message: President Biden will act to protect American and coalition personnel. At the same time, we have acted in a deliberate manner that aims to deescalate the overall situation in eastern Syria and Iraq."
Kirby said the US airstrikes "destroyed multiple facilities at a border control point used by a number of Iranian- backed militant groups".
Further details were not immediately available.
Biden administration officials condemned the February 15 rocket attack near the city of Irbil in Iraq's semi-autonomous Kurdish-run region, but as recently as this week officials indicated they had not determined for certain who carried it out.
Officials have noted that in the past, Iranian-backed Shiite militia groups have been responsible for numerous rocket attacks that targeted US personnel or facilities in Iraq.
Kirby had said on Tuesday Iraq was in charge of investigating the February 15 attack.
A little-known Shiite militant group calling itself Saraya Awliya al-Dam, Arabic for Guardians of Blood Brigade, claimed responsibility for the attack. A week later, a rocket attack in Baghdad's Green Zone appeared to target the US Embassy compound, but no one was hurt.
The frequency of attacks by Shiite militia groups against US targets in Iraq diminished late last year before Biden's inauguration, though Iran is now pressing America to return to Tehran's 2015 nuclear deal.
The US under the previous Trump administration blamed Iran-backed groups for carrying out the attacks. Tensions soared after a Washington-directed drone strike that killed top Iranian General Qassem Soleimani and powerful Iraqi militia leader Abu Mahdi al-Muhandis last year.
Trump had said the death of a US contractor would be a red line and provoke US escalation in Iraq. The December 2019 killing of a US civilian contractor in a rocket attack in Kirkuk sparked a tit-for-tat fight on Iraqi soil that brought the country to the brink of a proxy war.
US forces have been significantly reduced in Iraq to 2500 personnel and no longer partake in combat missions with Iraqi forces in ongoing operations against the Islamic State group.