WASHINGTON

U.S. President Donald Trump condemned a deadly Syrian regime attack in northwestern Syria's Idlib province during a telephone call with Turkish President Recep Tayyip Erdogan, the White House said Friday.

Trump "expressed his condolences and condemned yesterday’s attack that killed Turkish personnel in Syria," spokesman Judd Deere said in a statement.

"President Trump reaffirmed his support for Turkey’s efforts to de-escalate the situation in northwest Syria and avoid a humanitarian catastrophe," added Deere. "The two leaders agreed that the Syrian regime, Russia, and the Iranian regime must halt their offensive before more innocent civilians are killed and displaced."

Roughly 900,000 civilians have been displaced since the Syrian regime began its offensive on Idlib province with the assistance of Russian air power and Iranian-backed forces in December.

Late Thursday, at least 33 Turkish soldiers were martyred and tens of others injured in an airstrike by Assad regime forces in Idlib, just across Turkey’s southern border.

The Turkish soldiers are working to protect local civilians under a September 2018 deal with Russia under which acts of aggression are prohibited in the region.

But more than 1,300 civilians have been killed in attacks by Assad and Russian forces in the zone since then, as the cease-fire continues to be violated.

Thursday’s attack was one of a series since January on Turkish troops, with Turkish officials keeping their pledge that such assaults would not go unanswered.

The de-escalation zone is currently home to 4 million civilians, including hundreds of thousands displaced in recent years by regime forces throughout the war-torn country.

More than 1.7 million Syrians have moved near the Turkish border due to intense attacks.

Since the eruption of the Syria conflict in 2011, Turkey has taken in some 3.7 million Syrians who fled their country, making it the world’s top refugee-hosting country.