Two U.S. Army soldiers and a civilian interpreter were killed in Syria on Saturday by a suspected Daesh attacker who targeted a convoy of American and Syrian forces before being shot dead, the U.S. military said.

The attack was barely a month after Syria announced it had signed a political cooperation agreement with the U.S.-led coalition against Daesh, which coincided with Syrian President Ahmed al-Sharaa’s visit to the White House, Reuters reported.

The attacker was a member of the Syrian security forces, three local officials told Reuters. A Syrian Interior Ministry spokesperson told a state-run television channel that the man did not have a leadership role in the security forces.

“On December 10, an evaluation was issued indicating that this attacker might hold extremist ideas, and a decision regarding him was due to be issued tomorrow, on Sunday,” the spokesperson, Noureddine el-Baba, told Syrian television channel Al-Ikhbariya.

In a post on his Truth Social platform, U.S. President Donald Trump vowed “very serious retaliation,” mourning the loss of “three great patriots”. He described the incident in remarks to reporters as a “terrible” attack.

CENTRAL COMMAND SAYS THE ATTACKER WAS KILLED

Three U.S. soldiers were also wounded in the attack, the U.S. military’s Central Command said.

In a statement, Central Command said the attack by a lone gunman occurred “as the soldiers were conducting a key leader engagement” in the central Syrian town of Palmyra. “Partner forces” killed the attacker, U.S. Secretary of Defense Pete Hegseth wrote in a social media post.

A senior U.S. official said initial assessments indicated that Daesh probably carried out the attack, although the militant group did not immediately claim responsibility.

It took place in an area not controlled by the Syrian government, the official said.

Baba said Syria had warned about the possibility of an Daesh attack in that region but that “coalition forces did not take the Syrian warnings… into account.”

He said Syria would determine whether the attacker was linked to Daesh or merely subscribed to the group’s ideology.

The soldiers’ names will be withheld until 24 hours after the next-of-kin notification, the U.S. military said.

US ENVOY CONDEMNS THE ATTACK

Syrian state news agency SANA quoted a security source as saying two Syrian service personnel were injured, without providing further details. The source told SANA that American helicopters evacuated the injured to a U.S. base in Syria’s Al-Tanf region near the Iraqi border.

Tom Barrack, the U.S. ambassador to Turkey and special envoy to Syria, condemned the attack.

“We mourn the loss of three brave U.S. service members and civilian personnel and wish a speedy recovery to the Syrian troops wounded in the attack,” Barrack said in a statement. “We remain committed to defeating terrorism with our Syrian partners.”

The U.S.-led coalition has carried out air strikes and ground operations in Syria targeting Islamic State suspects in recent months, often with the involvement of Syria’s security forces. Syria last month also carried out a nationwide campaign arresting more than 70 people accused of links to the group.

The United States has troops stationed in northeastern Syria as part of a decade-long effort to help a Kurdish-led force there.