The United States is not deepening its role in Syria's civil war but will act defensively when needed, U.S. Defense Secretary Jim Mattis said on Thursday, as quoted by Reuters.
His comments came following U.S. air strikes against advancing militia backed by Syria's government.
"No. We are not increasing our role in the Syrian civil war. But we will defend our troops. And that is a coalition element made up of more than just U.S. troops, and so we will defend ourselves (if) people take aggressive steps against us," Mattis said, when asked about the strikes.
Earlier on Thursday, U.S.-led warplanes hit a pro-regime convoy in Syria that ignored warning shots.
U.S.-led aircraft struck the convoy as it headed toward a remote coalition garrison near the border with Jordan, said a U.S. defense official who was quoted by AFP.
"A convoy going down the road didn't respond to numerous ways for it to be warned off from getting too close to coalition forces in Al-Tanaf," the official told AFP on condition of anonymity.
"Then there was finally a strike against the lead portion of that movement," added the official.
The coalition said the strike had occurred "well inside" an established de-confliction zone northwest of the Al-Tanaf garrison, where British and U.S. commandos have been training and advising local forces fighting the Islamic State (ISIS) jihadist group.
The Syrian Observatory for Human Rights monitor said the strikes killed eight people, "most of them non-Syrian", and destroyed four vehicles.
The United States has been militarily involved in Syria since 2014, but has for the most part avoided engaging directly in the conflict.
Last month, however, President Donald Trump ordered an attack on Syria's Shayrat airbase, which the U.S. said was the launchpad for a chemical weapons attack that killed dozens of civilians in Idlib.
Syrian President Bashar Al-Assad has repeatedly denied his government has any chemical weapons after agreeing to give them up to international monitors in 2013.
In fact, Assad recently claimed that the Idlib attack was fabricated by the United States, insisting the Syrian army had already relinquished its chemical weapons reservoir.