"The US supports Turkey's efforts to maintain the Idlib ceasefire and we express condolences for the Turkish soldier killed as a result of shelling by the Assad regime," the United States Embassy Syria tweeted late Friday.
"We reiterate our condemnation of Assad's and Russia's escalatory attacks against the Idlib ceasefire zone."
One Turkish soldier was killed and three were wounded on Thursday when their observation post in Syria's Idlib region was attacked by shelling and mortar fire, the Turkish Defense Ministry said. In response, Turkish military retaliated in kind against the Assad regime forces.
In a statement, the Turkish Defense Ministry said Syrian regime forces carried out the attack on the post in the province's de-escalation zone.
The wounded were evacuated and have begun receiving medical treatment, the ministry said.
Russia's Ankara attache was summoned to military headquarters and was told that the attacks will be "punished in the strongest way," the ministry noted.
The Turkish Armed Forces (TSK) sent reinforcements to the area last night, as the area has been targeted several times by Assad regime forces over the past three months.
It was the sixth such attack near the observation post, with similar attacks by the regime also reported on April 29, May 4, 12, 31, and June 8.
Idlib, the last opposition last enclave in Syria, had a pre-war population of 1.5 million. The number swelled to around 3 million with new refugee waves after it was designated a "de-escalation zone" under the Astana agreement between Turkey, Russia and Iran in May 2017 that paved the way for a permanent political solution in Syria. The Turkish military set up 12 observation posts in Idlib's de-escalation zone after the ninth round of Astana-hosted peace talks.