Two U.S. Army soldiers and an American civilian interpreter were killed on Saturday, the Pentagon announced.

Three additional U.S. soldiers sustained injuries in the attack near Palmyra, Pentagon spokesman Sean Parnell stated, which occurred as the soldiers carried out ongoing operations in the region alongside Syrian government troops.

A Pentagon official informed TIME that the attack took place in an area outside Syrian government control, with an initial assessment deeming it “likely perpetrated by ISIS.”

Noureddine el-Baba, a spokesperson for the Syrian Interior Ministry, told state-run TV channel Al-Ikhbariya that the attacker was a member of government security forces already under investigation.

“On December 10, an evaluation concluded this attacker might hold extremist ideologies, and a decision regarding him was set to be issued tomorrow, Sunday,” Baba noted.

Three local officials also told Reuters the attacker was a member of Syrian government security forces, the agency reported.

President Donald Trump honored the soldiers in brief remarks to reporters at the White House Saturday afternoon, calling them “three great patriots.” When asked about U.S. retaliation, the president stated: “We will retaliate.”

In a statement denouncing the attack, Defense Secretary Pete Hegseth said the attacker was killed by “partner forces,” referencing the Syrian army.  

“Let it be clear: if you target Americans—anywhere on earth—you will spend your remaining short, anxious days knowing the U.S. will hunt you down, find you, and kill you without mercy,” Hegseth said. 

Syria’s state news agency reported two Syrian military personnel were also injured in the attack. 

Tom Barrack, U.S. ambassador to Turkey and the Trump Administration’s special envoy to Syria, also condemned the attack and paid tribute to the soldiers.

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

The attack follows just a month after Syria and the U.S.-led anti-ISIS coalition announced a political cooperation agreement during Syrian President Ahmed al-Sharaa’s visit to the White House.

Syrian Information Minister Hamza al-Mustafa said at the time that the agreement affirmed Syria’s role in “combating terrorism and supporting regional stability.”

President Barack Obama first deployed U.S. special operations forces to Syria in 2015 to advise and assist local Kurdish-led fighters battling ISIS, which was then a powerful force controlling large swaths of the country.

The Pentagon has previously stated that a core force of roughly 900 U.S. soldiers is currently deployed in eastern Syria to continue anti-ISIS operations.

However, President Trump has been vocal about his desire to withdraw troops from Syria, once referring to the country as “sand and death.” In 2019, during his first term, Trump ordered Defense Secretary James Mattis to withdraw all U.S. troops from Syria. Mattis opposed the plan and ultimately resigned in protest. Since then, Trump has withdrawn most troops from the country and later redeployed them.

Earlier this year, U.S. officials indicated the Trump Administration was drafting plans for a full troop withdrawal. The Pentagon declined to comment, but Trump stated at the time: “I don’t know who said that. I mean, I don’t know who said that, but we’ll decide on it. We’re not getting involved, we’re not engaged in Syria,” Trump responded. “Syria is its own mess. They have enough problems there; they don’t need us involved in everything.”

Trump has since developed a , Syria’s president and a former leader of an Al Qaeda-linked group.

Sharaa renounced Al Qaeda, rebranded his rebel forces, and rose to power one year ago this week, ousting Syrian dictator Bashar al-Assad and ending more than 50 years of Assad family rule.

This is a developing story.