The strikes mark the second time the Biden administration has taken military action in the region.
The U.S. military, under the direction of President Joe Biden, conducted airstrikes Sunday against what it said were "facilities used by Iran-backed militia groups" near the border between Iraq and Syria.
Pentagon Press Secretary John Kirby said the militias were using the facilities to launch unmanned aerial vehicle attacks against U.S. troops in Iraq.
Kirby said the U.S. military targeted three operational and weapons storage facilities — two in Syria and one in Iraq.
He described the airstrikes as "defensive," saying they were launched in response to the attacks by Iran-backed groups.
"The United States took necessary, appropriate, and deliberate action designed to limit the risk of escalation — but also to send a clear and unambiguous deterrent message," Kirby said.
Sunday's strikes mark the second time the Biden administration has taken military action in the region. In February, the U.S. launched airstrikes against facilities in Syria, near the Iraqi border, that it said were used by Iranian-backed militia groups.
The Pentagon said those strikes were retaliation for a rocket attack in Iraq in February that killed one civilian contractor and wounded a U.S. service member and other coalition troops.
At that time, Biden said Iran should view his decision to authorize U.S. airstrikes in Syria as a warning that it can expect consequences for its support of militia groups that threaten U.S. interests or personnel.
"You can't act with impunity. Be careful," Biden said when a reporter asked what message he had intended to send.
On Sunday, Kirby said Biden "has been clear that he will act to protect U.S. personnel. Given the ongoing series of attacks by Iran-backed groups targeting U.S. interests in Iraq, the President directed further military action to disrupt and deter such attacks."
The Pentagon spokesman added: "As a matter of international law, the United States acted pursuant to its right of self-defense. The strikes were both necessary to address the threat and appropriately limited in scope."
House Speaker Nancy Pelosi said in a statement Sunday that the U.S. airstrikes "appear to be a targeted and proportional response to a serious and specific threat," adding, "Protecting the military heroes who defend our freedoms is a sacred priority."